Best effort support for Hazelcast 4

[snicoll]

Spring Boot 2.3 still provides dependency management for Hazelcast 3. There are a number of changes in Hazelcast 4 that require us to adapt some integration code.

Unfortunately, the hazelcast team has decided to merge hazelcast-client in the main hazelcast jar, breaking our opt-in arrangement for auto-configuring an HazelcastInstance in client mode.

We've discussed some options in #20856 but we're missing some API to provide a full support for it, see this comment.

This issue is about making sure we support Hazelcast 4 the best we can if a user decides to override our dependency management.

The health indicator is broken due to API change. And the metrics support most likely require us to go the reflection route as well.

[snicoll]

I would have to call the constructor of HazelcastCacheMetrics by reflection now as the signature is not backward compatible.