RFR: 8315585: Optimization for decimal to string [v10]

[Shaojin Wen]

> I submitted PR #15555 before, and there were too many changes. I split it into multiple PRs with small changes. This one is one of them.
> 
> this PR removed the duplicate code for getChars in BigDecimal#StringBuilderHelper, i also make performance faster.
> Please review and don't hesitate to critique my approach and patch.

Shaojin Wen has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains 10 additional commits since the last revision:

 - Merge remote-tracking branch 'upstream/master' into optim_decimal_to_string_x1
 - remove JLA
 - recipe ("\1.\1\1")
 - Use StringConcatFactory.makeConcatWithConstants
 - use % calculate lowInt
 - refactor based on @cl4es 's review
 - fix from @cl4es 's review
 - fix from @cl4es 's review
 - refactor based on @liach 's review
 - optimize BigDecimal.toString

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/16006/files
  - new: https://git.openjdk.org/jdk/pull/16006/files/a17a106c..d5cbd7e9

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=16006&range=09
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=16006&range=08-09

  Stats: 35483 lines in 1139 files changed: 21247 ins; 7201 del; 7035 mod
  Patch: https://git.openjdk.org/jdk/pull/16006.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16006/head:pull/16006

PR: https://git.openjdk.org/jdk/pull/16006