hyundai openpilot long jerky accel/decel behavior at stop

### Describe the bug

Not sure if this is a model issue, or a Hyundai op long issue (did not experience this on older 0.8 releases of OP with hyundai op long). This behavior occurs a lot when behind a lead car, or when stopped at a red light, on both experimental mode and regular op long. The car will come to a stop (sometimes a little too far from the lead), then in rapid succession accel/decel and repeat, resulting in a jerky movement & requiring disengagement. The route provided is in experimental mode, and the behavior is shown at both a red light and with a lead. Was testing the nav branch, but this issue occurs pretty much on any master-based branch that allows for hyundai op long.

Radar tracks are enabled.

Stopped with lead car - 03:18:08
Stopped at red light - 09:24:02

### Which car does this affect?

2021 Hyundai Sonata

### Provide a route where the issue occurs

b0af2fff166d80fe|2023-06-12--09-14-42

### openpilot version

0.9.3 - f0c1e000c6ef09e61232e6afb4c3a658035afbb9

### Additional info

_No response_

Start by replaying route b0af2fff166d80fe|2023-06-12--09-14-42 on openpilot 0.9.3 for the 2021 Hyundai Sonata, focusing on 03:18:08 and 09:24:02. Compare the stopped-with-lead and stopped-at-red-light behavior, and consider the issue complete when the repeated rapid acceleration and deceleration no longer occurs.

Written by the indexing model from the issue text.