RFR: 8277497 Last column cell in the JTAble row is read as empty cell [v4]

[Artem Semenov]

> Testing https://bugs.openjdk.java.net/browse/JDK-8271071 
> Step to reproduce 
> 1) Run SwingSet2 in JDK 18 ( I used b24 ) 
> 2) Enable Voiceover. 
> 3) Select JTable demo 
> 4) Click any row in the table or select the first row . Observe that row is selected & VoiceOver reads the column values or navigate the columns one by one by pressing tab key. When the focus reaches the last column ( Favourite Food ) Observe that column value is read as null. If you hear the same then the bug is reproduced.

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

  Probably it should somehow ask the icon itself about possible description? I guess the JLabel should work similar to Icon/ImageIcon/AccessibleImageIcon/etc when the text is empty but the icon is set. But I am not sure that the iicons are supported by the a11y in Swing, for example how the reader will cover the simple Icon? Will it say something?

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/6538/files
  - new: https://git.openjdk.java.net/jdk/pull/6538/files/09d3fa57..2199bd53

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=6538&range=03
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=6538&range=02-03

  Stats: 11 lines in 1 file changed: 8 ins; 2 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6538.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6538/head:pull/6538

PR: https://git.openjdk.java.net/jdk/pull/6538