RFR: 8315999: Improve Date toString performance [v13]

[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:

  simplify LocalDate::getChars

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/15658/files
  - new: https://git.openjdk.org/jdk/pull/15658/files/d3ad4906..b7a3528c

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=15658&range=12
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=15658&range=11-12

  Stats: 6 lines in 1 file changed: 2 ins; 0 del; 4 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