RFR: 8327751: Convert javax/swing/JInternalFrame/6726866/bug6726866.java applet test to main [v2]

[Prasanta Sadhukhan]

> Conversion of manual applet test to main based using PassFailJFrame manual framework

Prasanta Sadhukhan has updated the pull request incrementally with two additional commits since the last revision:

 - Review comment update
 - Review comment update

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Changes:
  - all: https://git.openjdk.org/jdk/pull/18186/files
  - new: https://git.openjdk.org/jdk/pull/18186/files/ad5564c4..14679ff1

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=18186&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=18186&range=00-01

  Stats: 28 lines in 1 file changed: 4 ins; 5 del; 19 mod
  Patch: https://git.openjdk.org/jdk/pull/18186.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18186/head:pull/18186

PR: https://git.openjdk.org/jdk/pull/18186