RFR: 8315585: Optimization for decimal to string [v3]

[Shaojin Wen]

> Continue to complete PR #16006 and PR #21593 to improve BigDecimal::toString and BigDecimal::toPlainString performance and reduce duplicate code

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

  remove getChars(long, int, char[])

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Changes:
  - all: https://git.openjdk.org/jdk/pull/23310/files
  - new: https://git.openjdk.org/jdk/pull/23310/files/0e7b30be..cf67d847

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=23310&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=23310&range=01-02

  Stats: 65 lines in 1 file changed: 0 ins; 65 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/23310.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23310/head:pull/23310

PR: https://git.openjdk.org/jdk/pull/23310