RFR: 8308762: Metaspace leak with Instrumentation.retransform [v4]

[Jean-Philippe Bempel]

> Fix a small leak in constant pool merging during retransformation of a class. If this class has a catch block with `Throwable`, the class `Throwable` is pre-resolved in the constant pool, while all the other classes are in a unresolved state. So the constant pool merging process was considering the entry with pre-resolved class as different compared to the destination and create a new entry. We now try to consider it as equal specially for Methodref/Fieldref.

Jean-Philippe Bempel has refreshed the contents of this pull request, and previous commits have been removed. The incremental views will show differences compared to the previous content of the PR. The pull request contains one new commit since the last revision:

  Revert resolved class to unresolved for comparison
  
  remove is_unresolved_class_mismatch

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Changes:
  - all: https://git.openjdk.org/jdk/pull/14780/files
  - new: https://git.openjdk.org/jdk/pull/14780/files/05071a56..c1a2d7c7

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=14780&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=14780&range=02-03

  Stats: 2 lines in 1 file changed: 1 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/14780.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14780/head:pull/14780

PR: https://git.openjdk.org/jdk/pull/14780