api: Add (rudimentary) autopickling support

[FabioLuporini]

This is intended mostly for developers... for now

[codecov[bot]]

Codecov Report

:x: Patch coverage is 94.44444% with 4 lines in your changes missing coverage. Please review. :white_check_mark: Project coverage is 83.07%. Comparing base (20da795) to head (ab46578). :warning: Report is 14 commits behind head on main.

Files with missing lines	Patch %	Lines
devito/operator/operator.py	92.59%	2 Missing and 2 partials :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2775      +/-   ##
==========================================
+ Coverage   83.04%   83.07%   +0.02%     
==========================================
  Files         248      248              
  Lines       50452    50564     +112     
  Branches     4439     4447       +8     
==========================================
+ Hits        41900    42005     +105     
- Misses       7791     7798       +7     
  Partials      761      761              

Flag	Coverage Δ
pytest-gpu-aomp-amdgpuX	68.68% <47.27%> (-0.07%)	:arrow_down:
pytest-gpu-nvc-nvidiaX	69.22% <47.27%> (-0.06%)	:arrow_down:

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