RFR: 8338930: StringConcatFactory hardCoded string concatenation strategy [v5]

[Shaojin Wen]

> This is a follow-up to PR #20273, which improves performance when the number of parameters exceeds 20.
> 
> When the number of parameters is large, the possibility of reuse will be lower, so we can use the static concat method and write the length and coder directly into the bytecode to solve the performance regression problem.

Shaojin Wen has updated the pull request incrementally with two additional commits since the last revision:

 - reuseThreshold -> cacheThreshold
 - Revert "optimize for CompactStrings is off"
   
   This reverts commit a9fa264afd9fa625ef29357a7ca8559ce9c5fea4.

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Changes:
  - all: https://git.openjdk.org/jdk/pull/20675/files
  - new: https://git.openjdk.org/jdk/pull/20675/files/a9fa264a..871f67fc

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=20675&range=04
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=20675&range=03-04

  Stats: 7 lines in 1 file changed: 0 ins; 1 del; 6 mod
  Patch: https://git.openjdk.org/jdk/pull/20675.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20675/head:pull/20675

PR: https://git.openjdk.org/jdk/pull/20675