Make undulator gap flyable

[Relm-Arrowny]

Fixes #1469 #1261

• Change Apple2Val to be float
• Added undulatorBase for safeUndulatorMover.
• Added MotorWithoutStop
• GapSafeUndulatorUnstoppable to overwrite motor set method to allow flyable.
• Added overwrite prepare function in UndulatorGap to check min_velocity before prepare.

Instructions to reviewer on how to test:

1. Check test cover use cases.
2. run test.
3. Confirm test passes.

Checks for reviewer

• Would the PR title make sense to a scientist on a set of release notes
• If a new device has been added does it follow the standards
• If changing the API for a pre-existing device, ensure that any beamlines using this device have updated their Bluesky plans accordingly
• Have the connection tests for the relevant beamline(s) been run via dodal connect ${BEAMLINE}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.12%. Comparing base (00af332) to head (c9bbabc).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1470   +/-   ##
=======================================
  Coverage   99.12%   99.12%           
=======================================
  Files         283      286    +3     
  Lines       10736    10781   +45     
=======================================
+ Hits        10642    10687   +45     
  Misses         94       94           

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[olliesilvester]

Logic looks good but as far as I can see this is doing the same thing as the standard ophyd-async motor.

I still think we should create a new SafeMotor in dodal/ophyd-async which is a subclass of the standard motor, and gives the behaviour that you need. It would simplify this device quite a bit now

[Relm-Arrowny]

Now that I have typed it out, probably for another issue to do and not for this ticket...

Why wait, it is done but this https://github.com/bluesky/ophyd-async/pull/1152/files is breaking test.

[oliwenmandiamond]

Looks much better, but you will also have to mirror this for the tests and split that into its own parts