batches: clean up SSBC execution button and options
Created by: courier-new
Implements the UI from EM3 designs for execution options based on this screen:
https://user-images.githubusercontent.com/8942601/154166719-8acbb051-0d66-4f1d-a417-4a302b2863eb.mov
I chose to omit the second "Run spec with options" button that appears in the designs for now since there is ongoing discussion/disagreement about whether it makes sense to include it.
I'm loving using the animated accordion dropdown everywhere so I generalized it to be able to set its own expanded height and repurposed it into another Wildcard hook.
Test plan
This feature is experimental behind a feature flag and will not impact existing customers, so I only went as far as to verify the intended functionality locally myself.