fix(protocol-designer): update logic to add modules and fixtures with plate reader

[koji]

Overview

update logic to add modules and fixtures with plate reader and align ui with the latest design

• for onboarding flow, pd allows users to set only 1 plate reader and plate reader will be placed on B3
• for staging area, when a user sets a plate reader, available slots of staging area in select fixtures screen is 3 because of the above requirements. available slots are A3 (because trash bin can be placed column 1 slots), C3, D3
• remove dropdown from plate reader

design

the related thread
https://opentrons.slack.com/archives/C0866FUHXGQ/p1737665141057879

close AUTH-1287

Test Plan and Hands on Testing

• create a new protocol and set plate reader -> plate reader on B3
• create a new protocol and set plate reader -> available slots for staging area are 3 deck view displays plate reader on B3, 3 staging areas and trash bin is on A1
  if staging area's quantity is 1 or 2, plate reader on B3, trash bin on A3, and staging areas on C3 and D3
• create a new protocol and do not add plate reader -> available slots for staging area are 4 and deck view displays 4 staging areas and trash bin is on A1

Changelog

• update utils and its test
• remove dropdown menu from plate reader's list item

Review requests

Risk assessment

mid since this PR modify the logic for module selection and fixture selection