mgr/dashboard: Add /health/snapshot api

mgr/dashboard: Add /health/snapshot api

Fixes https://tracker.ceph.com/issues/72609

- The current minimal API relies on fetching data from osdmap and pgmap.
- These commands produce large, detailed payloads that become a performance bottleneck and impact scalability, especially in large clusters.
- To address this, we propose switching to the ceph snapshot API using ceph status command, which retrieves essential information directly from the cluster map.
- ceph status is significantly more lightweight compared to osdmap/pgmap, reducing payload sizes and processing overhead.
- This change ensures faster response times, improves system efficiency in large deployments, and minimizes unnecessary data transfer.
- update tests

Signed-off-by: Afreen Misbah <afreen@ibm.com>