Merge topic 'doc-test-RunCMake'

0dbf2c24bf Tests/RunCMake: Document how to write multi-step test cases
61a08b0856 Tests/RunCMake: Document commands/variables available to RunCMakeTest scripts
aebf6b8b29 Tests/RunCMake: Clarify documentation of platform-specific output matching
c2f8a6729f Tests/RunCMake: Rename "sub-test" terminology to "case"
0add7a802f Tests/RunCMake: Organize README as multiple sections
aff4dc47c4 Tests/RunCMake: Cross-reference README from main Tests/README

Acked-by: Kitware Robot <kwrobot@kitware.com>
Merge-request: !9548