fix(instance): fetch local_storage_max_size from Instance API

[Mia-Cross]

#5379 was supposed to keep the field local_storage_max_size for the json output but the field was not present in the PCU so it got left out.

This PR restores the previous behavior and fetches the information from the Instance API, along with the max number of file systems, which are now the 2 fields that are still retrieved from this API and not the PCU.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 50.36%. Comparing base (7881ee1) to head (db3ef50).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #5496   +/-   ##
=======================================
  Coverage   50.36%   50.36%           
=======================================
  Files         325      325           
  Lines       77384    77385    +1     
=======================================
+ Hits        38973    38974    +1     
  Misses      36933    36933           
  Partials     1478     1478           

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