Intern CassandraServer instances

General

Before this PR: ImmutableCassandraServer instances are created and used as Set elements & Map keys heavily, and would benefit from canonicalizing as there should be a relatively small, generally fixed number of Cassandra servers.

After this PR: Follow on to #6065 to reduce the number of live CassandraServer instances and simplify equals checks to identity equality. ==COMMIT_MSG== Intern CassandraServer instances

Weakly intern instances as there should be a relatively small, generally fixed number of Cassandra servers. ==COMMIT_MSG==

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Does this PR need a schema migration?

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Please tag any other people who should be aware of this PR: @jeremyk-91 @sverma30 @raiju

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Type See change types. Select one:

• [ ] Feature
• [x] Improvement
• [ ] Fix
• [ ] Break
• [ ] Deprecation
• [ ] Manual task
• [ ] Migration

Description Intern CassandraServer instances

Weakly intern instances as there should be a relatively small, generally fixed number of Cassandra servers.

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Big +1 to this.

As a concrete example, here's an heap dump from an OOM of one of our highest volume services. We have 23,000 instances of ImmutableCassandraServer.

Released 0.686.0