Conversion for zoom and microns per pixel

[adaudon]

In oav_parameters.py, there was an error when OAVConfigBeamCenter would run get_parameters() whenever the user clicked on the Move on Click button.
The um_xy and bc_xy had different types for their keys.
um_xy was giving integer strings while bc_xy was giving float strings.

So a change was made to convert um_xy to float strings which allowed the code to work as the keys now matched.

The issue might be related to the move to the daq config server?

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.13%. Comparing base (5824ccd) to head (8958030).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2059   +/-   ##
=======================================
  Coverage   99.13%   99.13%           
=======================================
  Files         337      337           
  Lines       13079    13080    +1     
=======================================
+ Hits        12966    12967    +1     
  Misses        113      113           

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[jacob720]

I think the type issues should also be fixed by this DiamondLightSource/daq-config-server#174, which means the zoom config will have it's own pydantic model with specified types.

[adaudon]

Once daq-config-server has that PR pushed, can remove this if needed to help prevent unintentional bugs. Not sure when it'll be pushed though so merging change for now.