RFR: 8343629: More MergeStore benchmark [v2]

[Shaojin Wen]

> 1. Added the putBytes4 benchmark, which corresponds to StringBuilder appendNull
> 2. Optimized the putChars4/setInt/setLong series of benchmarks to reduce extra overhead and more accurately reflect performance differences.

Shaojin Wen has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains five commits:

 - from @eme64 add MergeStoresDisabled
 - Merge remote-tracking branch 'upstream/master' into merge_store_bench_202410
 - Merge remote-tracking branch 'upstream/master' into merge_store_bench_202410
 - Merge branch 'master' into merge_store_bench_202410
 - add putBytes4 and improved put

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Changes: https://git.openjdk.org/jdk/pull/21659/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21659&range=01
  Stats: 320 lines in 1 file changed: 76 ins; 51 del; 193 mod
  Patch: https://git.openjdk.org/jdk/pull/21659.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21659/head:pull/21659

PR: https://git.openjdk.org/jdk/pull/21659