add actions to provide list of crush rules

[Robert Gildein]

It would be very useful to have action, which will provide list of ceph
crush rules.
In my opinion the function `ceph osd crush rule dump` should be perfect
for this.

Expected output:
```bash
juju run-action --wait ceph-mon/0 get-crush-rules
action-id: 09563275-87bc-4224-81ef-8282ad7e9d63
results:
    [(0, 'replicated_rule'), ...]
status: completed
...

```

[Billy Olsen (billy-olsen)]

Can you elaborate a bit what the use case is for providing the crush rules? Not disagreeing that there's use or not, but I'd like to understand the full use case for this.

[Robert Gildein (rgildein)]

This action will be used by juju-verify to check ceph-osd units. The main
reason is to gather information about crush rule, such as failure domain
and device class. Device class will be used to filter OSDs, ie ceph-osd
units and failure domain to verify that replication number for certain
pools will be preserved.

For more information you can have a look on this PR [1].

---
[1]: https://github.com/canonical/juju-verify/pull/56

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/c/openstack/charm-ceph-mon/+/835636

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/c/openstack/charm-ceph-mon/+/835636
Committed: https://opendev.org/openstack/charm-ceph-mon/commit/37105f11cdf1cb21948a24905e9d76f945aa4ee2
Submitter: "Zuul (22348)"
Branch: master

commit 37105f11cdf1cb21948a24905e9d76f945aa4ee2
Author: Robert Gildein <email address hidden>
Date: Tue Mar 29 16:21:56 2022 +0200

    Add list-crush-rules action

    This action provides a list of crush rules defined in CEPH clusters.

    Closes-bug: #1957458
    Change-Id: I2a5fdae776e00d869a624e1107ab42cf69bb2f50