Upgrade to VTK 9.1

See merge request iMSTK/iMSTK!739

Improve build system to streamline application integration

See merge request iMSTK/iMSTK!702

The application of "vtk-8.2.cmake" patch was obsoleted by commit
f796986e (REFAC: VTK 9 and greater dependence, task graph timing
chart disabled, data replacements, example updates)

Consistently using "mark_as_superbuild" along side the declaration
of the associated option or cache entry facilitates maintenance by
helping ensure value are consistently passed to the inner build.

For example, it fixes the passing of these two options:

* iMSTK_ENABLE_CUDA_BACKEND: Introduced in 5e90bbce (ENH: Enable CUDA
  in CMake configuration)

* iMSTK_SWIG_PINNED_ARRAY: Introduced in c2b5429e (ENH: add pinned array;
  add cmake option to choose between marshal array and pinned array)

Unless option have to be passed using the command line, this is the
recommended approach to pass options. It avoids "command line length issues".

This commit sets the cache variable prior configuring the outer
build (SUPERBUILD=ON) and it makes sure it is also propagated
down to the inner project.

This commit sets the cache variable prior configuring the outer
build (SUPERBUILD=ON) and it makes sure it is also propagated
down to the inner project.

The variable is currently used only in Wrappers project and was originally
introduced in 6acfa41f (COMP: Build audio only on windows).

This commit is a follow up of 35940011 (ENH: Update imstkSolveDependencies
module based on commontk/Artichoke@4176c39f9) where the variable should
have been originally removed.

Reports messages like the following when OPENHAPTICS_ROOT_DIR is not defined
and is being initialized based on the OH_SDK_BASE environment variable:

  [...]
  -- Checking if OH_SDK_BASE env. variable is defined
  -- Checking if OH_SDK_BASE env. variable is defined - TRUE
  -- Checking if OH_SDK_BASE env. variable is set to existing path
  -- Checking if OH_SDK_BASE env. variable is set to existing path - TRUE
  -- Setting OPENHAPTICS_ROOT_DIR to C:/OpenHaptics/Developer/3.4.0
  -- SuperBuild - First pass - done
  [...]

This commit works around a regression introduced in 5e3a7f46 (COMP: Support setting
custom SOURCE_DIR and BINARY_DIR vars) leading to the configuration error
copied below.

In the case of the OpenHaptics project, this led to always have the value
of the SOURCE_DIR parameter associated with the "imstk_add_external_project"
call to be ignored.

Error:

  CMake Error at C:/Program Files/CMake/share/cmake-3.20/Modules/ExternalProject.cmake:2847 (message):
    No download info given for 'OpenHaptics' and its source directory:

     E:/iMSTKProper/buildWin64/External/OpenHaptics/src

    is not an existing non-empty directory.  Please specify one of:

     * SOURCE_DIR with an existing non-empty directory
     * DOWNLOAD_COMMAND
     * URL
     * GIT_REPOSITORY
     * SVN_REPOSITORY
     * HG_REPOSITORY
     * CVS_REPOSITORY and CVS_MODULE
  Call Stack (most recent call first):
    C:/Program Files/CMake/share/cmake-3.20/Modules/ExternalProject.cmake:3681 (_ep_add_download_command)
    CMake/Utilities/imstkAddExternalProject.cmake:103 (ExternalProject_add)
    CMake/External/External_OpenHaptics.cmake:40 (imstk_add_external_project)
    CMake/Utilities/imstkSolveDependencies.cmake:868 (include)
    CMake/Utilities/imstkSolveDependencies.cmake:942 (ExternalProject_Include_Dependencies)
    CMake/External/CMakeLists.txt:70 (ExternalProject_Include_Dependencies)

Removes the use of NO_DEFAULT_PATH introduced in a709a89b (Cmake updates
for proper generation of iMSTKConfig.cmake) in favor of CONFIG and consistently
use CONFIG in both CMakeLists.txt and iMSTKConfig.

Requiring the GTest config file ensures the configuration succeeds by
preventing the FindGTest module provided by CMake from being used.

Removing the use of NO_DEFAULT_PATH allows to build iMSTK against a system
version of GTest (starting with Ubuntu 21.04 released in April 2021, the
libgtest-dev package includes GTestConfig.cmake)