mgr/dashboard: Replace dashboard service

mgr/dashboard: Replace dashboard service

This splits out the collection of health and log data from the
/api/dashboard/health controller into /api/health/{full,minimal} and
/api/logs/all.

/health/full contains all the data (minus logs) that /dashboard/health
did, whereas /health/minimal contains only what is needed for the health
component to function. /logs/all contains exactly what the logs portion
of /dashboard/health did.

By using /health/minimal, on a vstart cluster we pull ~1.4KB of data
every 5s, where we used to pull ~6KB; those numbers would get larger
with larger clusters. Once we split out log data, that will drop to
~0.4KB.

Fixes: http://tracker.ceph.com/issues/36675
Signed-off-by: Zack Cerza <zack@redhat.com>