<i18n dev> RFR: 8291660: Grapheme support in BreakIterator [v5]

[Naoto Sato]

> This is to enhance the character break analysis in `java.text.BreakIterator` to conform to the extended grapheme cluster boundaries defined in https://www.unicode.org/reports/tr29/#Grapheme_Cluster_Boundaries. A corresponding CSR has also been drafted, as there will be behavioral changes with this modification.

Naoto Sato has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains ten additional commits since the last revision:

 - Reverted the index checking fix
 - Removed character break data which is no longer needed
 - Merge branch 'master' into JDK-8291660-graphemes
 - Changed the paragraph to @implSpec
 - Reverting the fix to BreakIterator.isBoundary()
 - Fixing JCK failures
 - Addressing review comments
 - 8291660: Grapheme support in BreakIterator
 - 8291660: Add a method to stream extended grapheme clusters in a String

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Changes:
  - all: https://git.openjdk.org/jdk/pull/9991/files
  - new: https://git.openjdk.org/jdk/pull/9991/files/06cfc222..2f31d417

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=9991&range=04
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=9991&range=03-04

  Stats: 74365 lines in 1082 files changed: 32063 ins; 34006 del; 8296 mod
  Patch: https://git.openjdk.org/jdk/pull/9991.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9991/head:pull/9991

PR: https://git.openjdk.org/jdk/pull/9991