Merge topic 'vs-sln'

6a77c80834 cmGlobalVisualStudioGenerator: Consolidate solution generation methods
6b1c101410 cmGlobalVisualStudioGenerator: Adopt more solution generation methods
772cf917c1 cmGlobalVisualStudio71Generator: Remove this now-unnecessary class
3882718872 VS: Decouple solution generation from `.sln` file format
d67e7d2726 VS: Factor out Visual Studio `Version` enumeration
76266f9df6 cmGlobalVisualStudioGenerator: Adopt some solution generation methods
d52eb1d083 cmGlobalVisualStudioGenerator: Remove unused folder support rules
50f87b4bf2 cmGlobalGenerator: Simplify collection of targets under a project()
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Acked-by: Kitware Robot <kwrobot@kitware.com>
Merge-request: !11196