Save task state info in the ctx for checkpoint

[superstar54]

The engine saves the task state in the extras so that it can be accessed from outside the engine. However, this will create a mismatch when the engine process is restored from a checkpoint.

This PR saves the task state information in the context so that it can be restored from a checkpoint. The state info is also stored separately in the extras of the WorkGraph process node for each task so that we can query it. For the process node, we serialize it so that it can also be saved into the extras.

In order to interact with the running WorkGraph Engine, we need to use rpc_send to send a custom message to the engine.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 61.11111% with 7 lines in your changes missing coverage. Please review.

Project coverage is 79.48%. Comparing base (5937b88) to head (f1e4ff6).
Report is 40 commits behind head on main.

Files	Patch %	Lines
aiida_workgraph/engine/workgraph.py	61.53%	5 Missing ⚠️
aiida_workgraph/utils/control.py	33.33%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #245      +/-   ##
==========================================
+ Coverage   75.75%   79.48%   +3.73%     
==========================================
  Files          70       65       -5     
  Lines        4615     4807     +192     
==========================================
+ Hits         3496     3821     +325     
+ Misses       1119      986     -133     

Flag	Coverage Δ
python-3.11	79.40% <61.11%> (+3.73%)	⬆️
python-3.9	79.44% <61.11%> (+3.70%)	⬆️

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