Update save-panda to use DeviceManager

[noemifrisina]

Fixes #2144

As all beamlines with a panda have been moved to use DeviceManager, the old way of looking for factories has been removed from this script.

Instructions to reviewer on how to test:

1. Check tests pass
2. Try running save-panda on a beamline network and verify it can save the configuration file correctly. Run it again on main and verify it fails there.

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

❌ Patch coverage is 90.00000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 99.15%. Comparing base (9dad391) to head (0889ed0).

Files with missing lines	Patch %	Lines
src/dodal/plans/save_panda.py	90.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2154      +/-   ##
==========================================
- Coverage   99.16%   99.15%   -0.01%     
==========================================
  Files         353      353              
  Lines       13832    13839       +7     
==========================================
+ Hits        13716    13722       +6     
- Misses        116      117       +1     

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