RFR: 8271071 accessibility of a table on macOS lacks cell navigation [v3]

[Artem Semenov]

> We've extended the current implementation of TableAccessibility to make sure that individual cells are voiced when navigating with the keyboard.

Artem Semenov has updated the pull request incrementally with one additional commit since the last revision:

  It is not clear why we should manage columns without children. Would it be better if you investigate it separately, and here you do not remove this method?

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/5466/files
  - new: https://git.openjdk.java.net/jdk/pull/5466/files/6460deb3..c462fefa

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=5466&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=5466&range=01-02

  Stats: 55 lines in 1 file changed: 55 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5466.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5466/head:pull/5466

PR: https://git.openjdk.java.net/jdk/pull/5466