RFR: 8299595: Remove terminally deprecated JavaFX GTK 2 library

[Thiago Milczarek Sayao]

Simple PR to remove gtk2 library compilation and loading.

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Commit messages:
 - Remove gtk2
 - Merge branch 'openjdk:master' into master
 - Merge branch 'openjdk:master' into master
 - Merge branch 'openjdk:master' into master
 - Merge branch 'openjdk:master' into master
 - Merge branch 'openjdk:master' into master
 - Merge branch 'openjdk:master' into master
 - Merge branch 'openjdk:master' into master
 - Merge branch 'openjdk:master' into master
 - Merge branch 'openjdk:master' into master
 - ... and 18 more: https://git.openjdk.org/jfx/compare/23004367...80aac162

Changes: https://git.openjdk.org/jfx/pull/999/files
 Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=999&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8299595
  Stats: 127 lines in 5 files changed: 9 ins; 104 del; 14 mod
  Patch: https://git.openjdk.org/jfx/pull/999.diff
  Fetch: git fetch https://git.openjdk.org/jfx pull/999/head:pull/999

PR: https://git.openjdk.org/jfx/pull/999