Tests: Refactor RunCMake.File_Generate to drop RunCMake_TEST_FILE

Drop use of RunCMake_TEST_FILE and pass the test file in through a
definition in RunCMake_TEST_OPTIONS.
Tests: Refactor RunCMake.include_directories to drop RunCMake_TEST_FILE

Drop use of RunCMake_TEST_FILE and pass the test file in through a
definition in RunCMake_TEST_OPTIONS.
Tests: Drop broken and now unused RunCMake_TEST_FILE option

We cannot use -DRunCMake_TEST=${RunCMake_TEST_FILE} because test cases
use project(${RunCMake_TEST}) and the project name cannot be a path to a
file.  The parent and grandparent commits removed the only uses of the
option.  Drop it now.
Tests: Speed up RunCMake.include_directories test

Remove unnecessary language initializations.  Change the main
CMakeLists.txt project() call to specify NONE.  Use enable_language(CXX)
instead of project() in cases that need it to avoid enabling C too.
Merge topic 'test-speedup-RunCMake.include_directories' into next

9998d78d Tests: Speed up RunCMake.include_directories test
6eee5d74 Tests: Drop broken and now unused RunCMake_TEST_FILE option
f0f15b93 Tests: Refactor RunCMake.include_directories to drop RunCMake_TEST_FILE
8707814e Tests: Refactor RunCMake.File_Generate to drop RunCMake_TEST_FILE