ceph-mixin: fix linting issue and add cluster template support

ceph-mixin: fix linting issue and add cluster template support

Fix most of the issues reported by dashboards-linter:
- Add matcher/template for job (and also cluster)
- use $__rate_interval everywhere

Also this change all the irate functions to rate as most of irate where
not actually used correctly. While using irate on graph for instance you
can easily miss some of the metrics values as irate only take the two
last values and the query steps can be quite large if you want a graph
for a few hours/a day or more.

Fixes: https://tracker.ceph.com/issues/55003
Signed-off-by: Arthur Outhenin-Chalandre <arthur.outhenin-chalandre@cern.ch>
ceph-mixin: add config with matchers and tags

Signed-off-by: Arthur Outhenin-Chalandre <arthur.outhenin-chalandre@cern.ch>