RFR: 8271071 accessibility of a table on macOS lacks cell navigation [v5]

[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 refreshed the contents of this pull request, and previous commits have been removed. The incremental views will show differences compared to the previous content of the PR. The pull request contains one new commit since the last revision:

  The biggest problem i have is that the new logic reverts the mechanic of the selection mode of the table - when no selection mode set it announces the content of all the cells in the current row and when either row or column selection mode is set it only announces the content of a single cell. Also when only cell selection is allowed it announces row as dimmed which is strange.

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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/110f4f1a..248e2c64

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=5466&range=04
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=5466&range=03-04

  Stats: 774 lines in 14 files changed: 508 ins; 136 del; 130 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