qa: Add rgw singleton test to crimson

qa: Add rgw singleton test to crimson

This adds singleton tests of rgw to crimson. In classical OSD both
ubuntu and centos build are supported. However the crimson OSD only
provide centos build so cannot symlink all the files directly.

Instead of linking entire subdirectories the crimson suite uses
selective symlinks for the required yaml files.

Fixes: https://tracker.ceph.com/issues/73947
Signed-off-by: Kautilya Tripathi <kautilya.tripathi@ibm.com>