RFR: 8339492: StackMapDecoder::writeFrames makes lots of allocations

[David M. Lloyd]

Please review this change, which reduces the number of allocations in `StackMapDecoder::writeFrames` by using a sorted array instead of a `TreeMap<Integer, ...>` to sort and uniquify entries before writing.

Tested using `StackMapsTest`.

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Commit messages:
 - 8339492: StackMapDecoder::writeFrames makes lots of allocations

Changes: https://git.openjdk.org/jdk/pull/20841/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=20841&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8339492
  Stats: 30 lines in 1 file changed: 19 ins; 1 del; 10 mod
  Patch: https://git.openjdk.org/jdk/pull/20841.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20841/head:pull/20841

PR: https://git.openjdk.org/jdk/pull/20841