os/bluestore: update priorities and nicks of bluestore perf counters

os/bluestore: update priorities and nicks of bluestore perf counters

These perf counters do not show up in telemetry unless they are set to a "useful" priority or higher. Fetching these counters in telemetry may help to diagnose problems with RocksDB / BlueFS prefetching / insufficient cache sizes.

Signed-off-by: Laura Flores <lflores@redhat.com>
(cherry picked from commit 8790f04c5469d86daebb3bbe1eb780a86b7404ce)

Note: This backport (and the original PR) exposed an extra 34 perf counters/OSD to Prometheus. Given Pacific is a stable release and not to add that much extra load we are adapting this backport and only exposing the 2 required perf-coun>