RFR: 8309751: Duplicate constant pool entries added during default method processing [v3]

[Coleen Phillimore]

> This uses Ashutosh's patch to avoid adding duplicate constant pool entries during default method processing, with one change to make it conditional if not needed. I tested this locally and started writing a test, but writing a test is more difficult because duplicate constant pool entries don't actually violate the spec.
> 
> Tested with tier1-4 and ran some startup performance benchmarks on the patch.

Coleen Phillimore has updated the pull request incrementally with one additional commit since the last revision:

  Renamed to some more helpful names, also add a couple of comments.

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Changes:
  - all: https://git.openjdk.org/jdk/pull/18548/files
  - new: https://git.openjdk.org/jdk/pull/18548/files/f8fc3ee3..8e8059ab

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=18548&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=18548&range=01-02

  Stats: 16 lines in 2 files changed: 3 ins; 0 del; 13 mod
  Patch: https://git.openjdk.org/jdk/pull/18548.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18548/head:pull/18548

PR: https://git.openjdk.org/jdk/pull/18548