RFR: 8372974: Add missing @Override annotations in "com.sun.java.swing.plaf.gtk" package [v2]

[Sergey Bylokhov]

> This patch adds missing `@Override` annotations to methods in the `com.sun.java.swing.plaf.gtk` package that override methods from a superclass or interface.
> Only source annotations are added; there are no behavioral changes.
> 
> The previous patch for `com.sun.beans` can be found here: https://github.com/openjdk/jdk/pull/27887.
> 
> BTW, does anybody know why the gtk l&f is located in the shared code? Possibly we could move it to the unix folder, similar to how the windows l&f was moved to the windows folder in https://bugs.openjdk.org/browse/JDK-8189656 ?

Sergey Bylokhov has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains two additional commits since the last revision:

 - Merge branch 'openjdk:master' into gtkover
 - gtkover

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/28624/files
  - new: https://git.openjdk.org/jdk/pull/28624/files/604699c9..ee5c2ebc

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=28624&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=28624&range=00-01

  Stats: 47241 lines in 779 files changed: 31241 ins; 11897 del; 4103 mod
  Patch: https://git.openjdk.org/jdk/pull/28624.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28624/head:pull/28624

PR: https://git.openjdk.org/jdk/pull/28624