RFR: 8309751: Duplicate constant pool entries added during default method processing [v2]

[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:

  Added a comment and did some renaming to make it clearer what this is doing.

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Changes:
  - all: https://git.openjdk.org/jdk/pull/18548/files
  - new: https://git.openjdk.org/jdk/pull/18548/files/92cd6639..f8fc3ee3

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=18548&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=18548&range=00-01

  Stats: 8 lines in 1 file changed: 1 ins; 1 del; 6 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