RFR: 8090456: Focus Management [v2]

[Andy Goryachev]

> Public APIs for focus traversal and the focus traversal policy:
> 
> https://github.com/andy-goryachev-oracle/Test/blob/main/doc/FocusTraversal/FocusTraversal.md
> 
> This work is loosely based on the patch
> https://cr.openjdk.org/~jgiles/8061673/

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 seven additional commits since the last revision:

 - review comments
 - Merge remote-tracking branch 'origin/master' into 8090456.focus.traversal
 - review comments part 1
 - Merge remote-tracking branch 'origin/master' into 8090456.focus.traversal
 - Merge remote-tracking branch 'origin/master' into 8090456.focus.traversal
 - whitespace
 - 8090456: focus traversal

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

Changes:
  - all: https://git.openjdk.org/jfx/pull/1555/files
  - new: https://git.openjdk.org/jfx/pull/1555/files/4f168952..ddd3b281

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jfx&pr=1555&range=01
 - incr: https://webrevs.openjdk.org/?repo=jfx&pr=1555&range=00-01

  Stats: 2245 lines in 32 files changed: 1137 ins; 1022 del; 86 mod
  Patch: https://git.openjdk.org/jfx/pull/1555.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1555/head:pull/1555

PR: https://git.openjdk.org/jfx/pull/1555