RFR: 8376627: Remove AppContext from javax/swing/plaf/metal classes

[Phil Race]

Remove AppContext from Metal L&F

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Commit messages:
 - 8376627

Changes: https://git.openjdk.org/jdk/pull/29474/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=29474&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8376627
  Stats: 529 lines in 10 files changed: 2 ins; 505 del; 22 mod
  Patch: https://git.openjdk.org/jdk/pull/29474.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/29474/head:pull/29474

PR: https://git.openjdk.org/jdk/pull/29474