monitoring/ceph-mixin: scope test queries per dashboard

monitoring/ceph-mixin: scope test queries per dashboard

get_dashboards_data() keeps every query in a single map keyed by
"<panel title>-<legendFormat>", but that id is not unique: several
dashboards have a panel titled "IOPS", "OSDs" or "Throughput". The
dashboard read last overwrites the earlier entry, so one query shadows
another and never gets tested. glob() walks the files in filesystem
order, so which query survives, and whether the test passes, depends on
readdir.

run-tox-promql-query-test hit this in "Test IOPS Read"
(ceph-cluster.feature): the scenario feeds ceph_osd_op_r but the id
resolved to a CephFS pool panel.

    FAILED:
      expr: "sum(rate(ceph_pool_rd{cluster=~"mycluster|",  pool_id=~"UNSET VARIABLE"}[1m]))", time: 1m,
          exp:"{} 2.5E+01"
          got:"nil"
    HOOK-ERROR in after_scenario: AssertionError:

pool_id is "UNSET VARIABLE" because the scenario does not set $mdatapool,
and no ceph_pool_rd series were fed, so the query returns nil. It only
fails when readdir returns cephfsdashboard after ceph-cluster-advanced,
so the earlier change that walked nested rows and made the winner
deterministic did not fix it; it fixed which query wins, not that the
wrong one can win.

Key the queries per dashboard (data['queries'][<dashboard>][<id>]) and
have each .feature name its dashboard in a Background step. The lookup is
confined to that dashboard, so a title/legend used elsewhere no longer
shadows it. A duplicate within one dashboard is still an error, unless it
is in a collapsed row.

ceph-cluster.feature covers ceph-cluster-advanced; the rest map to one
dashboard each.

Signed-off-by: Kefu Chai <k.chai@proxmox.com>