Updating design for edit and add plan Modal for flexible majors

[23langloisj]

❓Problem: Currently the edit plan modal for flexible majors looks like this:

We want this to be more reflective of the design from the figma: https://www.figma.com/design/yUflVFVxjMynm7gGymLpQY/%F0%9F%8F%97-Current-Work?node-id=8516-48102

The add plan modal design should also be updated to follow the same logic, most of which should be directly transferrable from the edit plan changes.

Ignore any functionality for Minors and completely ignore concentrations at the moment but please still include the advanced edit dropdown.