RFR: 8364007: Add no-argument codePointCount method to CharSequence and String [v14]

[Tatsunori Uchino]

> Adds `codePointCount()` overloads to `String`, `Character`, `(Abstract)StringBuilder`, and `StringBuffer` to make it possible to conveniently retrieve the length of a string as code points without extra boundary checks.
> 
> 
> if (superTremendouslyLongExpressionYieldingAString().codePointCount() > limit) {
>     throw new Exception("exceeding length");
> }
> 
> 
> Is a CSR required to this change?

Tatsunori Uchino has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 20 commits:

 - Merge remote-tracking branch 'origin/master' into codepoint-count
 - Fix comments
 - Don't use removed `Character::codePointCount` overload
 - Update year in copyright
 - Fix double empty lines
 - Remove `Character.codePointCount()`
 - Replace "unpaired surrogates" with "isolated surrogate code units"
   
   https://www.unicode.org/versions/Unicode17.0.0/core-spec/chapter-3/#G1654
   https://www.unicode.org/charts/PDF/UDC00.pdf
 - Remove `Character.codePointCount` overload
 - Rename parameter names from `a` to `seq`
   
   `chars` is too confusing with `char`
 - Improve JavaDoc
   
   Co-authored-by: Chen Liang <liach at openjdk.org>
 - ... and 10 more: https://git.openjdk.org/jdk/compare/681e4ec8...198b3188

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Changes: https://git.openjdk.org/jdk/pull/26461/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=26461&range=13
  Stats: 80 lines in 7 files changed: 67 ins; 0 del; 13 mod
  Patch: https://git.openjdk.org/jdk/pull/26461.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26461/head:pull/26461

PR: https://git.openjdk.org/jdk/pull/26461