mgr/cephadm: split host cache entries if they exceed max mon store entry size

mgr/cephadm: split host cache entries if they exceed max mon store entry size

If the json blob we attempt to store for a host entry
exceeds the max mon store entry size, we become unable
to continue to store that hosts information in the
config key store. This means we only ever have the
information from the last time the json blob was
under the size limit each time the mgr fails over,
resulting in a number of stray host/daemon warnings
being generated and very outdated information being
reported by `ceph orch ps` and `ceph orch ls` around
the time of the failover

Signed-off-by: Adam King <adking@redhat.com>
(cherry picked from commit ffe61afc2b5e6c2f4db1001e5288dcd8f995e570)

Resolves: rhbz#2345474