[TRACKING ISSUE] Continue trying if initial membership event retrieval fails and client is failover [API-2171]

The tracking issue for the Java side PR.

See https://github.com/hazelcast/hazelcast/pull/26009 for details.

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As reported in https://hazelcast.atlassian.net/browse/API-2171, the client was not continuing trying next clusters if the connected cluster fails to send initial membership event in time. I added a check about client being failover in the conn. manager and conditionally handle the case.

This PR also adds required internal getters/APIs used in the test FailoverClusterMembershipEventTest in the EE PR https://github.com/hazelcast/hazelcast-enterprise/pull/6874

This tracking issue points to the Java-side PR 26009 and the EE test FailoverClusterMembershipEventTest in PR 6874. Start by reading those linked changes and the API-2171 report; done means the client continues trying the next cluster when initial membership-event retrieval fails during failover.

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