RFR: 8315999: Improve Date toString performance [v6]

[温绍锦]

> improve date toString performance, includes:
> 
> java.util.Date.toString
> java.util.Date.toGMTString
> java.time.Instant.toString
> java.time.LocalDate.toString
> java.time.LocalDateTime.toString
> java.time.LocalTime.toString

温绍锦 has updated the pull request incrementally with one additional commit since the last revision:

  revert un-related changes

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/15658/files
  - new: https://git.openjdk.org/jdk/pull/15658/files/2a617db5..26d7c7c0

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=15658&range=05
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=15658&range=04-05

  Stats: 14 lines in 1 file changed: 11 ins; 2 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/15658.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15658/head:pull/15658

PR: https://git.openjdk.org/jdk/pull/15658