Fix many warnings during build

[8Keep]

And also ban any new unchecked warnings with werror, so we don't have any regressions.

I know there are a decent number of suppressed ones in the repo, I will try to burn down some of those next.

[gemini-code-assist]

Code Review

This pull request modernizes the codebase by updating Gradle build scripts, adding generics to core utilities and rendering pipelines, and transitioning to newer FrameBuffer and Texture APIs. It also addresses compiler warnings and marks legacy methods as deprecated. Feedback focuses on critical API compatibility regressions in the Android modules where newer methods were introduced without version guards, potentially breaking support for older API levels. Additionally, several suggestions were provided to include @SuppressWarnings annotations on new helper methods to fully resolve unchecked cast warnings.

[github-actions]

🖼️ Screenshot tests have failed.

The purpose of these tests is to ensure that changes introduced in this PR don't break visual features. They are visual unit tests.

📄 Where to find the report:

• Direct Download: screenshot-test-report
• Alternatively, go to the failed run summary > Artifacts > screenshot-test-report
• Download the zip and open jme3-screenshot-tests/build/reports/ScreenshotDiffReport.html

⚠️ If you didn't expect to change anything visual:
Fix your changes so the screenshot tests pass.

✅ If you did mean to change things:
Review the replacement images in jme3-screenshot-tests/build/changed-images to make sure they really are improvements and then replace and commit the replacement images at jme3-screenshot-tests/src/test/resources.

✨ If you are creating entirely new tests:
Find the new images in jme3-screenshot-tests/build/changed-images and commit the new images at jme3-screenshot-tests/src/test/resources.

Note; it is very important that the committed reference images are created on the build pipeline, locally created images are not reliable. Similarly tests will fail locally but you can look at the report to check they are "visually similar".

See https://github.com/jMonkeyEngine/jmonkeyengine/blob/master/jme3-screenshot-tests/README.md for more information

Contact @richardTingle (aka richtea) for guidance if required