RFR: 8355177: Speed up StringBuilder::append(char[]) via UTF16::compress & Unsafe::copyMemory [v2]

[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 use the intrinsic method StringUTF16.compress and Unsafe.copyMemory instead of the character copy of the char-by-char loop to improve the speed.

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

  putCharsUnchecked

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Changes:
  - all: https://git.openjdk.org/jdk/pull/24773/files
  - new: https://git.openjdk.org/jdk/pull/24773/files/ee356d3a..ec6482b0

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=24773&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=24773&range=00-01

  Stats: 2 lines in 1 file changed: 0 ins; 0 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