Add monitor function

[superstar54]

For user's convenience, we provide a dedicated MonitorFunction class that inherits from PyFunction.
The user only needs to write a normal function, which returns True when the monitoring condition is met.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 91.93548% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 88.51%. Comparing base (a212e7a) to head (256d3c4).

Files with missing lines	Patch %	Lines
src/aiida_pythonjob/calculations/tasks.py	87.87%	4 Missing ⚠️
src/aiida_pythonjob/calculations/pyfunction.py	95.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #52      +/-   ##
==========================================
+ Coverage   88.37%   88.51%   +0.14%     
==========================================
  Files          22       22              
  Lines        1213     1263      +50     
==========================================
+ Hits         1072     1118      +46     
- Misses        141      145       +4     

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