ceph-mixin: Update monitoring mixin

ceph-mixin: Update monitoring mixin

Update `rate()` queries to be more accurate. The use of `irate()` leads
to misleading graphs because it only looks at the last 2 samples over
the selected time range step interval. Also use `$__rate_interval`
consistently in order to scale over short and long time ranges.
* Replace `irate()` with `rate()` to avoid sample bias.
* Use `$__rate_interval` consistently.
* Update auto_count/min to provide higher detail graphs.

Fixes: https://tracker.ceph.com/issues/72343
Signed-off-by: SuperQ <superq@gmail.com>
Signed-off-by: Ankush Behl <cloudbehl@gmail.com>