PD Bug: deleting labware -> wonky UI

[IanLondon]

Deleting a labware that is used in a step is an ugly experience

Steps to reproduce

1. Create some labware, tips, and a transfer step (for example), and save the step
2. Go to Deck Setup and delete the labware

• Labware dropdown isn't blank (whatever labware is on the top of the dropdown looks like it's selected)
• Well selection isn't disabled, clicking it shows the blank "Custom labware" plate

Expected behavior

• the labware dropdown should be blank.
• well selection should be cleared & disabled until a new labware is selected PD: Clear well selection when corresponding labware is deleted #2361
• It should still continue to generate the alert: "A step involves labware that has been deleted"

[IanLondon]

PR #2341 gets us 50% there, but I'm calling this ticket blocked because the part where selected wells gets cleared out would mean adding an independent path to updating forms. Discussed with @b-cooper and we agree that we should put this off at least until we do "user can save the form any time" behavior, and/or until we at least have a plan for the more flexible step form.

[IanLondon]

Splitting the punted part off to #2361 (clear well selection), so outside of that part, this ticket is finished