RFR: 8305780: javax/swing/JTable/7068740/bug7068740.java fails on Ubunutu 20.04

[Prasanta Sadhukhan]

Although not able to reproduce this locally or in mach5, it can happen when robot key movements start happening before frame is visible,
so added stability fixes like delay of 1s after frame is visible and key movements are done, added waitForIdle, increase autodelay time, added frame dispose also at end.

Several iterations of the test pass in all platforms. Link in JBS

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Commit messages:
 - 8305780: javax/swing/JTable/7068740/bug7068740.java fails on Ubunutu 20.04
 - 8305780: javax/swing/JTable/7068740/bug7068740.java fails on Ubunutu 20.04

Changes: https://git.openjdk.org/jdk/pull/13416/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=13416&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8305780
  Stats: 87 lines in 1 file changed: 28 ins; 30 del; 29 mod
  Patch: https://git.openjdk.org/jdk/pull/13416.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13416/head:pull/13416

PR: https://git.openjdk.org/jdk/pull/13416