RFR: 8339492: StackMapDecoder::writeFrames makes lots of allocations [v2]

[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. It also adds a validation missed by the original implementation.
> 
> Tested using `StackMapsTest`.

David M. Lloyd has updated the pull request incrementally with one additional commit since the last revision:

  Review feedback: reject duplicate stack map entries

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Changes:
  - all: https://git.openjdk.org/jdk/pull/20841/files
  - new: https://git.openjdk.org/jdk/pull/20841/files/54b16010..04436b35

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=20841&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=20841&range=00-01

  Stats: 20 lines in 1 file changed: 3 ins; 14 del; 3 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