Use steer_p_gain for UpdateVelocity steer joint speed

[retinfai]

Summary

This PR uses the steer_p_gain to control steering joint speed for ackermann based vehicles using Twist to drive. Replicates logic from the UpdateAngle, which is steering only.

Checklist

• [x] Signed all commits for DCO
• [ ] 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)
• [ ] While waiting for a review on your PR, please help review another open pull request to support the maintainers

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

[retinfai]

cc @bperseghetti