Merge topic 'FILE_SET-update-generation-step'

dee8799d16 FileSet management: Introduce dedicated classes for generation
b45dcfd306 Extract cmTargetPropertyEntry class from cmGeneratorTarget class.
c362c4a7b5 cmTargetSourcesCommand: enhance arguments checks
c4c84ae0f7 cmFileSet: Enhance type management

Acked-by: Kitware Robot <kwrobot@kitware.com>
Tested-by: buildbot <buildbot@kitware.com>
Merge-request: !11698