Fix a few issues with passing non-serializable JSON

[FrederikBolding]

AbstractExecutionService will now properly guard against passing invalid JSON-RPC requests and BaseSnapExecutor will try to respond with an error if it receives an invalid JSON-RPC request that is deemed valid enough to respond.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (2143331) 95.99% compared to head (537815c) 96.04%.
Report is 2 commits behind head on main.

❗ Current head 537815c differs from pull request most recent head bf4d6b6. Consider uploading reports for the commit bf4d6b6 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1974      +/-   ##
==========================================
+ Coverage   95.99%   96.04%   +0.04%     
==========================================
  Files         263      265       +2     
  Lines        6149     6175      +26     
  Branches      989      992       +3     
==========================================
+ Hits         5903     5931      +28     
+ Misses        246      244       -2     

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