Provide a general purpose Hazelcast integration (i.e. not tied to caching).

Auto-configure a `HazelcastInstance` either based on the presence of a
`Config` bean or a configuration file. Said configuration file can be
specified explicitly or automatically found from default locations.

The cache integration already supports Hazelcast so it has been reworked
to automatically reuse an existing `HazelcastInstance` if available.

Closes gh-2942