RFR: 8178355: IdentityHashMap uses identity-based comparison for values everywhere except remove(K,V) and replace(K,V,V) [v4]

[liach]

> Explicitly implement `remove` and `replace` in `IdentityHashMap` to compare values by identity. Updated API documentation of these two methods ([Preview](https://cr.openjdk.java.net/~liach/8178355/IdentityHashMap.html#remove(java.lang.Object,java.lang.Object))) to mention such behavior.

liach has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains six additional commits since the last revision:

 - Move tests
 - Merge branch 'master' into fix/identityhashmap-default
 - Fix assertions
 - Revamp test and changes. Let ci run the tests
 - Fix indent
 - 8178355: IdentityHashMap uses identity-based comparison for values everywhere except remove(K,V) and replace(K,V,V)

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/8259/files
  - new: https://git.openjdk.java.net/jdk/pull/8259/files/fe91721d..c8468ce2

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=8259&range=03
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=8259&range=02-03

  Stats: 53894 lines in 1878 files changed: 35482 ins; 8470 del; 9942 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8259.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8259/head:pull/8259

PR: https://git.openjdk.java.net/jdk/pull/8259