Merge topic 'vs-slnx' into release-4.2

0c97912756 VS: Fix SLNX generation so .NET Core projects build in the IDE
7ce9185792 VS: Add include_external_msproject GUIDs for more project types
ab2ef244bd VS: Add include_external_msproject detection of `.njsproj` type
00db01ddcd Tests: Fix RunCMake.include_external_msproject .sln check failure

Acked-by: Kitware Robot <kwrobot@kitware.com>
Acked-by: Christian Lichtenberger <christian.lichtenberger@etm.at>
Merge-request: !11613