2MP from 8MP capturing

Captures an 8MP image to memory, downsamples it to 2MP, then saves to disk

Relies on !246 (merged) being merged first

Current issue with this is how often the capture_jpeg function hangs forever, effectively crashing the camera (see #355 (closed) #298 (closed) #299 (closed) #319)

Externally, relies on https://github.com/labthings/labthings-picamera2/compare/highres_arrays?expand=1 now merged

Scans now run fairly reliably if we decrease the --resize parameter during ongoing stitching, and if we only have one stitching thread running. Stitching at the end still crashes due to the size of the images we're trying to create closed by openflexure-stitching!52 (merged)

Closes #364 (closed) #413 (closed) #298 (closed) #303 (closed) #288 (closed) #358 (closed)

Merge checklist:

• All new/changed functions have up to date typehints and docstrings
• Any UI updates have a before and after screenshot in the MR description
• Unit testing of new functionality has similar or better coverage that similar existing code Removed because this adds a large amount of hardware specific code that cannot be tested on CI
• This code has been tested on a microscope
  • With webapp has been recompiled (if changed)
  • With updated settings JSON (if changed)
  • SmartScan and live stitching work

Before

After