RFR: 8361209: (bf) Use CharSequence::getChars for StringCharBuffer bulk get methods [v5]

[Brian Burkhalter]

> For `CharBuffer`s created from a `CharSequence`, use `CharSequence.getChars` to perform bulk gets instead of successively copying single characters.

Brian Burkhalter has updated the pull request incrementally with one additional commit since the last revision:

  8361209: Fix assertion added in previous commit

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/26251/files
  - new: https://git.openjdk.org/jdk/pull/26251/files/3c88dac7..11a73ffa

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=26251&range=04
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=26251&range=03-04

  Stats: 9 lines in 1 file changed: 0 ins; 7 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/26251.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26251/head:pull/26251

PR: https://git.openjdk.org/jdk/pull/26251