RFR: 8338041: Keyboard Navigation of JTable, Ctrl Shift RIGHT/LEFT doesn't follow native action in GTK L&F [v2]

[Tejesh R]

> In JTable, keyboard navigation keys Ctrl Shift RIGHT/LEFT doesn't follow native actions of Linux. In native the actions are extended to end of selected columns cells either LEFT/RIGHT but in swing gtk look and feel the selection is extended to one cell to left/right. This might be taken as reference of Windows OS since the same is observed in Windows native. Hence I have update the actions for Ctrl Shift RIGHT & LEFT. 
> Added automated test too. The fix is tested in CI and its fine.

Tejesh R 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 four additional commits since the last revision:

 - Updated review comments
 - Merge branch 'master' of https://git.openjdk.java.net/jdk into branch_8338041
 - Test updates
 - Key action modified + Automatic test added

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Changes:
  - all: https://git.openjdk.org/jdk/pull/20608/files
  - new: https://git.openjdk.org/jdk/pull/20608/files/ab34edf8..8c436fdd

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=20608&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=20608&range=00-01

  Stats: 151966 lines in 3309 files changed: 91575 ins; 44053 del; 16338 mod
  Patch: https://git.openjdk.org/jdk/pull/20608.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20608/head:pull/20608

PR: https://git.openjdk.org/jdk/pull/20608