Fixed JobStore.from_dict_spec so that the original dict_spec is not modified

[davidwaroquiers]

Fixed JobStore.from_dict_spec so that the original dict_spec is not modified.
The spec is now copied so that if this is used programmatically, the type is not removed from the original spec_dict, which may be used afterwards, (e.g. stored in a database), or if there is some validation by a pydantic schema.

@utf For information, this is making the jobflow-remote fail in some of the config cases.

Summary

Include a summary of major changes in bullet points:

• Modification of the internal _construct_store method so that the original dict_spec is not modified.

Additional dependencies introduced (if any)

None

TODO (if any)

None

Checklist

[codecov]

Codecov Report

Merging #331 (7fe62c6) into main (7e62e93) will not change coverage.
The diff coverage is 100.00%.

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #331   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           19        19           
  Lines         1429      1430    +1     
  Branches       361       361           
=========================================
+ Hits          1429      1430    +1     

Impacted Files	Coverage Δ
src/jobflow/core/store.py	100.00% <100.00%> (ø)

[utf]

Thanks!