RFR: 8376998: [macOS] Remove AppContext from AppEventHandler

[Phil Race]

This removes AppContext from the _AppEventHandler class used on macOS.

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Commit messages:
 - 8376998
 - 8376998

Changes: https://git.openjdk.org/jdk/pull/29534/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=29534&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8376998
  Stats: 49 lines in 2 files changed: 4 ins; 30 del; 15 mod
  Patch: https://git.openjdk.org/jdk/pull/29534.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/29534/head:pull/29534

PR: https://git.openjdk.org/jdk/pull/29534