mgr/dashboard/api: generate offline API docs

mgr/dashboard/api: generate offline API docs

Generate Sphinx documentation from OpenAPI YAML spec:
- Fixed Docs controller doc generation
- Now dashboard Python doesn't fails if dashboard/frontend/dist doesn't exist
- OpenAPI added to @ceph/api CODEOWNERS
- Renamed Ceph-Dashboard API to Ceph REST or RESTful API.
- OpenAPI Docs: fixed decorators and docstrings.
- Sphinx Docs: updated dashboard and dev ones.

Co-authored-by: Ernesto Puerta <epuertat@redhat.com>
Fixes: https://tracker.ceph.com/issues/45863
Signed-off-by: Courtney Caldwell <ccaldwel@redhat.com>
Signed-off-by: Ernesto Puerta <epuertat@redhat.com>