[WIP] Various Improvements

[Eric-Vin]

Description

Placeholder PR to track various Scenic improvements.

Driving Domain Behaviors:

• Added a pure pursuit lateral controller, which performs far better than the PID lateral controller.
• Revamped pedestrian behaviors, allowing them to walk around obstacles and other agents and avoid walking directly in front of moving vehicles. See the GIFs below for some examples.

General Improvements:

• Added apparent heading to X [from Y] scalar operator along with X ahead of Y, X behind Y, X left of Y, and X right of Y boolean operators.
• Added support for running behaviors in parallel.
• Added a new followFromTrajectory method which returns the entire trajectory followed instead of just the final point.
• Scenic now detects changes to the parser and will automatically re-build it when needed.

Bugfixes:

• Fixed order of lanes in backwards LaneGroup. Previously, backwards lane groups had this tuple in the opposite direction (element 0 farthest from the curb).

Examples

New Pedestrian Behaviors:

Issue Link

NA

Checklist

• I have tested the changes locally via pytest and/or other means
• I have added or updated relevant documentation
• I have autoformatted the code with black and isort
• I have added test cases (if applicable)

Additional Notes

NA