[desc] Execute pre & post process in the farm

[Alxiice]

PR description

pass

Implementation notes

• Create a add_method_flag decorator to be able to check whether a method is overloaded or not
• ...

Note to the reviewers

pass

[codecov]

Codecov Report

❌ Patch coverage is 81.81818% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 79.80%. Comparing base (cca5cc5) to head (aeac5c5).
⚠️ Report is 5 commits behind head on develop.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
meshroom/core/desc/node.py	81.81%	2 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #2984   +/-   ##
========================================
  Coverage    79.80%   79.80%           
========================================
  Files           64       64           
  Lines         8674     8685   +11     
========================================
+ Hits          6922     6931    +9     
- Misses        1752     1754    +2     

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