RFR: 8316104: Open source several Swing SplitPane and RadioButton related tests [v2]

[Tejesh R]

> Open sourcing these Swing SplitPane and RadioButton related tests:
> 
> javax/swing/JSplitPane/4147653/bug4147653.java
> javax/swing/JSplitPane/4870674/bug4870674.java
> javax/swing/JRadioButton/4823809/bug4823809.java

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 three additional commits since the last revision:

 - Review fix
 - Merge branch 'master' of https://github.com/openjdk/jdk into branch_8316104
 - Open sourcing few SplitPane and RadioButton test

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/15738/files
  - new: https://git.openjdk.org/jdk/pull/15738/files/4671cd9f..fe25033c

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=15738&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=15738&range=00-01

  Stats: 83825 lines in 3215 files changed: 47893 ins; 18833 del; 17099 mod
  Patch: https://git.openjdk.org/jdk/pull/15738.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15738/head:pull/15738

PR: https://git.openjdk.org/jdk/pull/15738