cpack: Add `CPACK_INSTALL_CMAKE_CONFIGURATIONS` variable

For the multi-configuration generators one can specify the list
of configurations to include in the package.

E.g. having a project, where debug libraries have a suffix to
distinct them from the release builds, one can build the package
containing both `Debug` and `Release` binaries.
32 jobs for feature/cpack-install-multiple-configurations
Status Job ID Name Coverage
  External
passed cdash

failed cmake-dash3win10-windows-release-ninja

passed cmake-hythloth-linux-debug-makefiles+sphinx

passed cmake-minoc-linux-release-lint-iwyu-tidy

passed cmake-moonshade-osx-debug-ninja

passed cmake-moonshade-osx-release-makefiles

passed cmake-terfin-windows-release-vs2019

passed ghostflow-check-master

passed ghostflow-stager

failed cmake-dash3win10-windows-release-ninja

failed cmake-dash3win10-windows-release-ninja

failed cmake-dash3win10-windows-release-ninja

00:20:01

passed cmake-hythloth-linux-debug-makefiles+sphinx

passed cmake-hythloth-linux-debug-makefiles+sphinx

passed cmake-hythloth-linux-debug-makefiles+sphinx

passed cmake-hythloth-linux-debug-makefiles+sphinx

00:44:23

passed cmake-minoc-linux-release-lint-iwyu-tidy

00:12:31

passed cmake-minoc-linux-release-lint-iwyu-tidy

passed cmake-minoc-linux-release-lint-iwyu-tidy

passed cmake-moonshade-osx-debug-ninja

passed cmake-moonshade-osx-debug-ninja

passed cmake-moonshade-osx-debug-ninja

00:22:10

passed cmake-moonshade-osx-debug-ninja

passed cmake-moonshade-osx-release-makefiles

00:11:39

passed cmake-moonshade-osx-release-makefiles

passed cmake-moonshade-osx-release-makefiles

passed cmake-moonshade-osx-release-makefiles

passed cmake-terfin-windows-release-vs2019

passed cmake-terfin-windows-release-vs2019

00:38:51

passed cmake-terfin-windows-release-vs2019

passed cmake-terfin-windows-release-vs2019

passed ghostflow-stager