mgr/DaemonServer: include mgr module options in config show output

'ceph config show/show-with-defaults mgr.<id>' omitted all mgr module
options because they are stored in PyModuleConfig, not in the daemon's
config map. This adds them to both commands.
Also adds an integration test to qa/workunits/mon/config.sh.

Fixes: https://tracker.ceph.com/issues/24458
Signed-off-by: Nitzan Mordechai <nmordech@ibm.com>