Fastcs eiger support

[DominicOram]

See https://github.com/DiamondLightSource/dodal/issues/700. This implements enough of the Eiger/Odin for us to prove that we can actually take some data with it. To completely cover all the capability of the ophyd device we need to do a lot, at least:

• https://github.com/bluesky/ophyd-async/issues/529
• https://github.com/bluesky/ophyd-async/issues/530
• https://github.com/bluesky/ophyd-async/issues/531
• https://github.com/bluesky/ophyd-async/issues/532

To Test

• Confirm unit tests pass
• Run the system tests as described in the system test directory, confirm they pass

Notes

• I'm particularly interested in someone who knows the intent of the detector architecture to review this to confirm it follows the pattern correctly.

[DominicOram]

Given the refactors in https://github.com/bluesky/ophyd-async/issues/405 and https://github.com/bluesky/ophyd-async/issues/551 I'm going to merge this as a MVP and park any further development on the other issues.