RFR: 8357696: Enhance code consistency: java.desktop/unix:sun

[Sergey Bylokhov]

This is a request to update the remaining parts of the java.desktop/unix package.
The sun.awt subpackage under java.desktop/unix was previously addressed by https://github.com/openjdk/jdk/pull/24941.

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The `java.desktop` module currently lacks proper use of the `@Override` annotation for methods and the `final` modifier for classes. While similar changes were previously made in the [JavaSound](https://github.com/openjdk/jdk/commit/e0c7d59246cf36644d494eced76e4b9d96ff1ded#diff-ae3e5f9c40fe25ef03e7a89844de174ef5c15e6179d769e2a4bcb7e73688c9b5), [java.desktop/windows](https://github.com/openjdk/jdk/pull/24170) (and some of the classes on demand), these changes are not as critical now due to the new jdk "encapsulation", but they are still useful for improving code consistency.

The public API was not affected so there is no need to worry about a CSR

Note: I will submit additional patches in this area later because:

1. Only lines with `@Override` and `final` were modified to keep the diff clear - header dates were not updated (that could be covered by one patch similar to [this](https://bugs.openjdk.org/browse/JDK-8345797))
2. I skipped adding `@Override` for anonymous classes

Any feedback or suggestions are welcome!

Here is a [link](https://patch-diff.githubusercontent.com/raw/openjdk/jdk/pull/25439.diff) to a simple diff file, it might be more convenient for reviewing the changes.

To download the diff file and filter only the modified lines you can use the following script:


curl -s https://patch-diff.githubusercontent.com/raw/openjdk/jdk/pull/25439.diff -o d.txt && grep -E '^+|^-' d.txt


The build was successful, and I ran all the open jtreg tests without issues. But it's possible that some closed tests may be affected by these changes. It would be good to verify this by mach5 to ensure everything works as expected.

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Commit messages:
 - Merge branch 'openjdk:master' into over_all_unix
 - final in java.desktop/unix
 - override in java.desktop/unix

Changes: https://git.openjdk.org/jdk/pull/25439/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=25439&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8357696
  Stats: 390 lines in 64 files changed: 294 ins; 0 del; 96 mod
  Patch: https://git.openjdk.org/jdk/pull/25439.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25439/head:pull/25439

PR: https://git.openjdk.org/jdk/pull/25439