RFR: 8296266: TextArea: Navigation breaks with RTL text [v3]

[Andy Goryachev]

> The fix uses character BreakIterator instead of the logic that relies on caretBounds/hitTest/rangeShape in TextInputControl.nextCharacterVisually().
> 
> I believe this is a more reliable method of navigation, as it behaves in sync with the jdk break iterator, thought it might work differently around grapheme clusters, considering a recent change JDK-8291660
> 
> This change also introduces TextInputControlHelper class (impl. detail) which gives access to character- and word- break iterators cached by TextInputControl (*some say* these iterators and associated editing logic should be a part of Content implementation, but that's a discussion for another day).

Andy Goryachev 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 six additional commits since the last revision:

 - Merge remote-tracking branch 'origin/master' into 8296266.navigation
 - naming changes only
 - Merge remote-tracking branch 'origin/master' into 8296266.navigation
 - added robot test
 - exposing cached break iterators
 - using break iterator

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

Changes:
  - all: https://git.openjdk.org/jfx/pull/1220/files
  - new: https://git.openjdk.org/jfx/pull/1220/files/94bba45e..36979b6a

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jfx&pr=1220&range=02
 - incr: https://webrevs.openjdk.org/?repo=jfx&pr=1220&range=01-02

  Stats: 3058 lines in 22 files changed: 2764 ins; 239 del; 55 mod
  Patch: https://git.openjdk.org/jfx/pull/1220.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1220/head:pull/1220

PR: https://git.openjdk.org/jfx/pull/1220