Merge topic 'ep-refactor-scripts'

5fbac2bb24 ExternalProject: Move inline scripts to separate files
8feaa41ee9 ExternalProject: Ensure _ep_set_directories records cmake paths
036517fe0b ExternalProject: Move existing step scripts to separate subdirectory

Acked-by: Kitware Robot <kwrobot@kitware.com>
Tested-by: buildbot <buildbot@kitware.com>
Merge-request: !6888