RFR: 8268225: Support :focus-visible and :focus-within CSS pseudoclasses [v9]

[Michael Strauß]

> This PR adds the `Node.focusVisible` and `Node.focusWithin` properties, as well as the corresponding `:focus-visible` and `:focus-within` CSS pseudo-classes.

Michael Strauß 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 23 additional commits since the last revision:

 - Merge branch 'master' into feature/focusvisible
 - Updated since tag
 - Update copyright headers
 - Merge branch 'master' into feature/focusvisible
 - fixed undeterministic test failures
 - minor wording change
 - restart github actions
 - Merge branch 'master' of https://github.com/mstr2/jfx into feature/focusvisible
 - changes per discussion, added test
 - wording
 - ... and 13 more: https://git.openjdk.java.net/jfx/compare/a6d4f5e5...0c7d6e72

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Changes:
  - all: https://git.openjdk.java.net/jfx/pull/475/files
  - new: https://git.openjdk.java.net/jfx/pull/475/files/bd57bbac..0c7d6e72

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jfx&pr=475&range=08
 - incr: https://webrevs.openjdk.java.net/?repo=jfx&pr=475&range=07-08

  Stats: 101583 lines in 580 files changed: 34334 ins; 31264 del; 35985 mod
  Patch: https://git.openjdk.java.net/jfx/pull/475.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx pull/475/head:pull/475

PR: https://git.openjdk.java.net/jfx/pull/475