Vehicle model steering angle limiting: clip to lateral accel while disengaged

[sshane]

If you engage with current angle above the max allowed angle for the current lateral accel limit, panda will block the instant snap down. Clip the requested angle while disengaged to this limit too.

• [ ] needs support in safety to allow this while disengaged, it just considers the hard-coded max angle we have currently

[sshane]

@devtekve feel free to take this over, writing the test that catches this change first, then testing the new behavior