mgr/telemetry: add the rocksdb version number to telemetry

mgr/telemetry: add the rocksdb version number to telemetry

Capturing the RocksDB version number in Telemetry would allow us to check that users are using the appropriate RocksDB version for their Ceph cluster. For instance, if a user is working in a Pacific cluster, but their RocksDB version is meant for Nautilus, that might be a problem.

It is strucured as "rocksdb_stats" --> "version" in anticipation of more stats that can will be added under "rocksdb_stats".

Signed-off-by: Laura Flores <lflores@redhat.com>