RFR: 8378202: Remove AppContext from XAWT classes

[Phil Race]

Remove AppContext from XAWT.

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Commit messages:
 - 8378202
 - 8378202

Changes: https://git.openjdk.org/jdk/pull/29804/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=29804&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8378202
  Stats: 44 lines in 4 files changed: 2 ins; 30 del; 12 mod
  Patch: https://git.openjdk.org/jdk/pull/29804.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/29804/head:pull/29804

PR: https://git.openjdk.org/jdk/pull/29804