RFR: 8355790: Enhance code consistency: java.desktop/unix:sun.awt

[Sergey Bylokhov]

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.

To make the code review process easier I have made the following changes:

1. I chose `java.desktop/unix:sun.awt` as the starting package because it contains a relatively small number of classes
2. 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/24941.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/24941.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.

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

Commit messages:
 - override in java.desktop/unix:sun.awt
 - final in java.desktop/unix:sun.awt

Changes: https://git.openjdk.org/jdk/pull/24941/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=24941&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8355790
  Stats: 748 lines in 105 files changed: 646 ins; 1 del; 101 mod
  Patch: https://git.openjdk.org/jdk/pull/24941.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/24941/head:pull/24941

PR: https://git.openjdk.org/jdk/pull/24941