Filter: increase test coverage

[scpeters]

🦟 Bug fix

Improve test coverage of the Filter classes, similar to #807

Summary

This increases test coverage based on suggestions from Gemini and uses static_cast<T> where needed to fix windows C4244 compiler warnings.

Summary of test coverage improvements

1. Set & Value Methods: added test coverage in OnePoleQuaternion, OnePoleVector3, and BiQuadVector3.
2. Fc: added test calls for Fc overloads in BiQuadVector3.
3. Multi-Step Process State Updates: call Process multiple times to exercise internal recursive feedback state updates.
4. Template Types: test float and int instantiations: OnePole<float>, OnePole<int>, BiQuad<float>, BiQuad<int>.

Backport Policy

• This is safe to backport to the following versions:
  • Jetty
  • Ionic
  • Harmonic
  • Fortress
• This should not be backported
• I am not sure
• Other (fill in yourself)

Checklist

• Signed all commits for DCO
• Added a screen capture or video to the PR description that demonstrates the fix (as needed)
• Added tests
• Updated documentation (as needed)
• Updated migration guide (as needed)
• Consider updating Python bindings (if the library has them)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
• Updated Bazel files (if adding new files). Created an issue otherwise.
• While waiting for a review on your PR, please help review another open pull request to support the maintainers
• Was GenAI used to generate this PR? If so, make sure to add "Assisted-by" to your commits. (See this policy for more info.)

Assisted-by: Gemini 3.6 Flash

Note to maintainers: Remember to use Squash-Merge and edit the commit message to match the pull request summary while retaining Signed-off-by and Generated-by messages.

Backports: If this is a backport, please use Rebase and Merge instead.