Merge pull request #42255 from tchaikov/wip-cmake-mgr-cleanup

cmake: install mgr module separately

Reviewed-by: Ernesto Puerta <epuertat@redhat.com>
Reviewed-by: Sebastian Wagner <sewagner@redhat.com>

diff --cc CMakeLists.txt
Simple merge

diff --cc src/pybind/mgr/CMakeLists.txt
Simple merge