mgr/prometheus: track individual healthchecks as metrics

mgr/prometheus: track individual healthchecks as metrics

This patch creates a health history object maintained in
the modules kvstore.  The history and current health
checks are used to create a metric per healthcheck whilst
also providing a history feature. Two new commands are added:
ceph healthcheck history ls
ceph healthcheck history clear

In addition to the new commands, the additional metrics
have been used to update the prometheus alerts

Fixes: https://tracker.ceph.com/issues/52638
Signed-off-by: Paul Cuzner <pcuzner@redhat.com>