The health endpoint histogram has a large amount of cardinality for a
simple endpoint. Introduce a new "Slim" set of buckets for `/health` to
reduce the metrics load on large deployments. Especially those that have
per-node DNS caching services.

Add a metric to count internal health check failures rather than use the
timeout value as side effect monitor of the check error. This avoids
incorrectly recording the timeout value if there is an error that is not
a timeout (ex. refused)
Signed-off-by: SuperQ <superq@gmail.com>