Create snapshots after robot load

[DominicOram]

We need to do snapshots and put them in ispyb

• We already do OAV snapshots for pin tip etc.
• We will need to add those snapshot lines to the robot load plan
• The ispyb callback will then need to pick up the path to this
• We don't have the off-axis webcam as a ophyd device yet, we can hopefully reuse the OAV - if this is more complicated spin into a new issue

Acceptance Criteria

• The snapshots are put into robot load as:
  

[DominicOram]

Note we don't have the beam position overlay in yet (potentially we could put this in the OAV itself?). For now don't worry about the beam position, we can add it in after if we need

[DominicOram]

The webcam image comes from http://i03-webcam1/axis-cgi/jpg/image.cgi. We will need to write a new device for this. See DiamondLightSource/dodal#435