This commit fixes a regression introduced in 0ffa63e9 (COMP: Add relevant
vars to iMSTKConfig to streamline config against a build-tree) by ensuring
REQUIRED parameter passed when finding iMSTK is not passed when looking up
vtkRenderingExternal and vtkRenderingOpenVR projects.

Introduce variables Libusb_DLL_DIR, Libusb_DLL_NAME, Libusb_LIB_DIR
and Libusb_LIB_NAME for use in application implementing their own
external  project including the ones provided by iMSTK.

* Use Libusb_PREFIX set in imstk_define_external_dirs and remove Libusb_PREFIX ivar
* Remove explicit setting of BINARY_DIR external project argument. It is
  not relevant since this external project download an archive.

Introduce variables FTD2XX_DLL_DIR, FTD2XX_DLL_NAME, FTD2XX_LIB_DIR
and FTD2XX_LIB_NAME for use in application implementing their own
external project including the ones provided by iMSTK.

It ensures the install subdirectory exists when custom location is
specified.

* Use FTD2XX_PREFIX set in imstk_define_external_dirs and remove FTD2XX_PREFIX ivar
* Remove explicit setting of BINARY_DIR external project argument. It is
  not relevant since this external project download an archive.

This commit ensures the iMSTKConfig file configured in an iMSTK build tree
includes variables like <proj>_DIR, <proj>_ROOT_DIR, <proj>_LIB_DIR to avoid
client project to have to specify these project are internal dependencies
of iMSTK.

This commit also:

* introduces iMSTK_VTK_DEPENDENCIES to avoid duplicating
  the list of required VTK components in iMSTKConfig.

* makes uses find_dependency to properly forward parameter like REQUIRED
  or QUIET.

* ensures variables CMAKE_DEBUG_POSTFIX and CMAKE_MODULE_PATH are restored
  to there original values after attempting to find the relevant dependencies.

This commit updates the project to specify the install commands
responsible to copy file to CMAKE_INSTALL_PREFIX only if *no*
custom install directory was specified.

It updates the logic to use g3log_INSTALL_DIR instead of CMAKE_INSTALL_PREFIX.

It ensures the install subdirectory exists when custom location is
specified.

This allows to integrate iMSTK in a project building the required VTK
module externally by leveraging VTKExternalModule.

See https://github.com/KitwareMedical/VTKExternalModule

Introduce variables OpenVR_DLL_DIR, OpenVR_DLL_NAME, OpenVR_LIB_DIR
and OpenVR_LIB_NAME for use in application implementing their own
external  project including the ones provided by iMSTK.

* Use OpenVR_PREFIX set in imstk_define_external_dirs and remove OPENVR_PREFIX ivar
* Remove explicit setting of BINARY_DIR external project argument. It is
  not relevant since this external project download an archive.

This commit updates the module to conditionally pass the "openvr" include
subdirectory specific to the OpenVR install tree generated by the OpenVR
external project specific to iMSTK.

Configuring iMSTK against an installation of OpenVR specified passing
option OpenVR_ROOT_DIR and OpenVR_INC_DIR is now supported.

This commit renames the project so that its name is consistent with
VTK established convention providing the vtkRenderingOpenVR module.

Increase robustness to support case when the option has not been declared
in application integrating iMSTK and re-using the external projects.

Removes obsolete setting of CMAKE_GENERATOR_* variables in imstk_add_external_project,
indeed these variables are now automatically passed to projects from within
the updated imstkSolveDependencies CMake module.

This commit updates the build system to follow the established CMake
convention.

It also allows the use of iMSTK custom find package in the context of
external project named after the library being integrated and avoid
target name conflicts.

References:

* Double colon in target name means ALIAS or IMPORTED target.

  Source: https://cmake.org/cmake/help/latest/policy/CMP0028.html

* This convention of double-colons gives CMake a hint that the name
  is an IMPORTED target when it is used by downstreams with the
  target_link_libraries() command. This way, CMake can issue a
  diagnostic if the package providing it has not yet been found.

  Source: https://cmake.org/cmake/help/latest/manual/cmake-packages.7.html

Similarly to the pair <package>_ROOT_DIR/<package>_LIB_DIR used by
"imstk_find_libary", this commit support specifying a custom include
subdirectory associated with "imstk_find_header".

This commit removes the requirement for systematically passing <package>_LIB_DIR
in addition of <package>_ROOT_DIR by setting <package>_LIB_DIR to "lib" if not
already defined.

This commit ensures library like "libusb" can be found on linux
by updating the list of accepted library suffix.

This commit ensures the custom find module can be used to set the
variable "<package>_INCLUDE_DIR" in the cache similarly to how the
"<package>_LIBRARY_<library>-<config>" are set.

This is particularly useful when integrating iMSTK in other packages
where the packages may have to be looked up prior configuring iMSTK.

This commit streamlines maintenance by ensuring the variable set by the
iMSTK custom find package modules are named after the package being
discovered.

It fixes warnings like the following:

```
  CMake Warning (dev) at /path/to/cmake-3.20.1-linux-x86_64/share/cmake-3.20/Modules/FindPackageHandleStandardArgs.cmake:438 (message):
    The package name passed to `find_package_handle_standard_args` (LIBUSB)
    does not match the name of the calling package (Libusb).  This can lead to
    problems in calling code that expects `find_package` result variables
    (e.g., `_FOUND`) to follow a certain pattern.
```

This commit ensures custom CMake/FindXXX.cmake package specifying that
the debug library should be the same as the release library are effectively
looking up the expect library to set the variable `${PACKAGE}_LIBRARY_${library}-DEBUG`.

Without this commit, running cmake specifying `--debug-find` argument
at configuration time incorrectly included USE_SYSTEM in the name of the
debug library to lookup.

For example, here is the output associated with Libusb reported on Linux:

```
$ cmake --debug-find .

[...]
  CMake Debug Log at /path/to/imstkFind.cmake:148 (find_library):
    find_library called with the following settings:

      VAR: Libusb_LIBRARY_libusb-1.0-DEBUG
      NAMES: "libusb-1.0USE_SYSTEM"
             "liblibusb-1.0USE_SYSTEM"
      Documentation: Path to a library.
      Framework
        Only Search Frameworks: 0
        Search Frameworks Last: 0
        Search Frameworks First: 0
      AppBundle
        Only Search AppBundle: 0
        Search AppBundle Last: 0
        Search AppBundle First: 0
      CMAKE_FIND_USE_CMAKE_PATH: 1
      CMAKE_FIND_USE_CMAKE_ENVIRONMENT_PATH: 1
      CMAKE_FIND_USE_SYSTEM_ENVIRONMENT_PATH: 1
      CMAKE_FIND_USE_CMAKE_SYSTEM_PATH: 1

    find_library considered the following locations:

      [...]
      /usr/local/sbin/(lib)libusb-1.0USE_SYSTEM(\.so|\.a)
      /usr/local/bin/(lib)libusb-1.0USE_SYSTEM(\.so|\.a)
      [...]

    The item was not found.

[...]
```

REFAC: Fix warning, Remove CollisionConstraint Enum

See merge request iMSTK/iMSTK!746

BUG: Fix enableBendConstraint for multi strided bend constraints & fix stride iteration

See merge request iMSTK/iMSTK!743

BUG: Add collision re-enabled

See merge request iMSTK/iMSTK!744

ENH: Toggle for vsync

See merge request iMSTK/iMSTK!742