RFR: 8352908: Open source several swing tests batch1

[Damon Nguyen]

Open-sourcing and standardizing several tests (JSplitPane JApplet JToolBar)

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Commit messages:
 - Initial add
 - Merge branch 'master' of github.com:DamonGuy/jdk
 - Merge branch 'master' of github.com:DamonGuy/jdk
 - Merge branch 'master' of github.com:DamonGuy/jdk
 - Initial commit for backout

Changes: https://git.openjdk.org/jdk/pull/24559/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=24559&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8352908
  Stats: 353 lines in 4 files changed: 353 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/24559.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/24559/head:pull/24559

PR: https://git.openjdk.org/jdk/pull/24559