Expose more plans to i04 BlueAPI

[olliesilvester]

David has requested that we expose a few more plans to i04's BlueAPI, specifically:

• Find beam centre at current zoom and at current transmission
• Optimise transmission for current zoom level
• Move scintillator in
• Move scintillator out.
  Note that for these last two we should just expose bluesky plan stubs and then call something like run_plan("mv", "scintillator", "IN"). Just need to make sure it's user-friendly for scientists since they won't be able to easily see the syntax