RFR: 8339635: StringConcatFactory optimization for CompactStrings off [v2]

[Shaojin Wen]

> A small optimization, when CompactStrings is turned off, the coder method is not generated, which improves the startup performance

Shaojin Wen has updated the pull request incrementally with one additional commit since the last revision:

  add java doc

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Changes:
  - all: https://git.openjdk.org/jdk/pull/20722/files
  - new: https://git.openjdk.org/jdk/pull/20722/files/067bb0dc..32979c13

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=20722&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=20722&range=00-01

  Stats: 3 lines in 1 file changed: 3 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/20722.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20722/head:pull/20722

PR: https://git.openjdk.org/jdk/pull/20722