Merge topic 'log_level_command'

23bbac941a Add cmake_language(GET_MESSAGE_LOG_LEVEL) sub command
2b6ef864e0 Move LogLevel enum out of cmake.h header

Acked-by: Kitware Robot <kwrobot@kitware.com>
Tested-by: buildbot <buildbot@kitware.com>
Merge-request: !7348