RFR: 8361209: (bf) Use CharSequence::getChars for StringCharBuffer bulk get methods [v2]

[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 problems due to ignoring slice offset

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Changes:
  - all: https://git.openjdk.org/jdk/pull/26251/files
  - new: https://git.openjdk.org/jdk/pull/26251/files/bed82d4b..fb5ea838

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=26251&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=26251&range=00-01

  Stats: 8 lines in 1 file changed: 2 ins; 0 del; 6 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