Merge topic 'import-std-refactor'

42d2d63235 c++modules: Copy props from BMI consumers more correctly
6d3e9d8220 c++modules: single import std target

Acked-by: Kitware Robot <kwrobot@kitware.com>
Tested-by: buildbot <buildbot@kitware.com>
Reviewed-by: Ben Boeckel <ben.boeckel@kitware.com>
Merge-request: !12193