RFR: 8364007: Add no-argument codePointCount method to CharSequence and String [v10]

[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 incrementally with one additional commit since the last revision:

  Fix double empty lines

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/26461/files
  - new: https://git.openjdk.org/jdk/pull/26461/files/c9719d4e..4f80009e

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=26461&range=09
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=26461&range=08-09

  Stats: 1 line in 1 file changed: 0 ins; 1 del; 0 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