* Unregister remote write queue manager specific metrics when stopping the
queue manager.
* Use DeleteLabelValues instead of Unregister to remove queue and watcher
related metrics when we stop them. Create those metrics in the structs
start functions rather than in their constructors because of the
ordering of creation, start, and stop in remote storage ApplyConfig.
* Add setMetrics function to WAL watcher so we can set
the watchers metrics in it's Start function, but not
have to call Start in some tests (causes data race).
Signed-off-by: Callum Styan <callumstyan@gmail.com>
e87449b59d