RFR: 8355177: Speed up StringBuilder::append(char[]) via Unsafe::copyMemory [v6]

[Shaojin Wen]

> In BufferedReader.readLine and other similar scenarios, we need to use StringBuilder.append(char[]) to build the string.
> 
> For these scenarios, we can Unsafe.copyMemory instead of the character copy of the char-by-char loop to improve the speed.
> 
> @RogerRiggs completed the optimization when the encoder is LATIN1 in PR #24967. This PR continues to complete the optimization when the encoder is UTF16.

Shaojin Wen has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 12 commits:

 - inline checkBoundsBeginEnd, from @RogerRiggs
 - inline putCharsUnchecked, from @RogerRiggs
 - Merge remote-tracking branch 'upstream/master' into optim_sb_append_chars_202504
 - copyright
 - Merge remote-tracking branch 'upstream/master' into optim_sb_append_chars_202504
   
   # Conflicts:
   #	src/java.base/share/classes/java/lang/AbstractStringBuilder.java
 - Merge remote-tracking branch 'upstream/master' into optim_sb_append_chars_202504
   
   # Conflicts:
   #	src/java.base/share/classes/java/lang/AbstractStringBuilder.java
 - Merge remote-tracking branch 'upstream/master' into optim_sb_append_chars_202504
   
   # Conflicts:
   #	src/java.base/share/classes/java/lang/StringUTF16.java
 - putCharsUnchecked
 - copyright
 - Using StringUTF16.compress to speed up LATIN1 StringBuilder append(char[])
 - ... and 2 more: https://git.openjdk.org/jdk/compare/50910576...2a45cfc1

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

Changes: https://git.openjdk.org/jdk/pull/24773/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=24773&range=05
  Stats: 42 lines in 2 files changed: 34 ins; 6 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/24773.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/24773/head:pull/24773

PR: https://git.openjdk.org/jdk/pull/24773