RFR: 8306566: Open source several clipboard AWT tests

[Alexander Zvegintsev]

Open sourcing few AWT clipboard tests.

Testing looks good.

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Commit messages:
 - initial

Changes: https://git.openjdk.org/jdk/pull/13595/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=13595&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8306566
  Stats: 864 lines in 6 files changed: 864 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/13595.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13595/head:pull/13595

PR: https://git.openjdk.org/jdk/pull/13595