RFR: 8336856: Optimize String Concat [v35]

[Shaojin Wen]

> This PR implements the same algorithm as the current generateMHInlineCopy based on bytecode to improve startup performance.

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

 - checkOverflow
 - highArity default 0
 - use MethodTypeDesc instead of MethodType
 - inlineThreshold parameter
 - use more idiomatic class-file API
 - rename SimpleStringBuilderStrategy to InlineHiddenClassStrategy

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Changes:
  - all: https://git.openjdk.org/jdk/pull/20273/files
  - new: https://git.openjdk.org/jdk/pull/20273/files/adc12ade..65a16e41

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=20273&range=34
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=20273&range=33-34

  Stats: 129 lines in 2 files changed: 18 ins; 25 del; 86 mod
  Patch: https://git.openjdk.org/jdk/pull/20273.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20273/head:pull/20273

PR: https://git.openjdk.org/jdk/pull/20273