RFR: 8306640: Open source several AWT TextArea related tests

[Tejesh R]

Open source few AWT TextArea related tests.

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

Commit messages:
 - Open sourced TextArea tests

Changes: https://git.openjdk.org/jdk/pull/13670/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=13670&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8306640
  Stats: 437 lines in 4 files changed: 437 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/13670.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13670/head:pull/13670

PR: https://git.openjdk.org/jdk/pull/13670