Metrics for HotRod client connection

[ahus1]

As we are using the remote Infinispan more intensively we would like to see metrics on the client connections (for example how many currently-in-use connections)

Infinispan Issue: https://issues.redhat.com/browse/ISPN-16394

As the backport for 15.x wasn't done, we'll wait for ISPN 16 to include it.

[ahus1]

@pruivo - I see that the parent issue was merged and then backported for ISPN 15.0.11, but then later reverted.

So we'll wait for a ISPN 15.1+ release for this to be available for Keycloak?

[pruivo]

Unfortunately, we need ISPN 16 since 15.1 or later won't be productized and RHBK cannot use it.