Fix an issue where errors would not correctly be returned

[FrederikBolding]

Fixes an issue where errors thrown inside the snap would not be correctly returned because they weren't JSON serializable. Instead, the JSON-RPC request would get no response and stall until it was timed out.

This was fixed by changing the pattern used to return errors when a response value is not valid JSON.

[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: +0.01% 🎉

Comparison is base (f865a28) 95.82% compared to head (db74c3c) 95.84%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1772      +/-   ##
==========================================
+ Coverage   95.82%   95.84%   +0.01%     
==========================================
  Files         239      239              
  Lines        5464     5465       +1     
  Branches      851      851              
==========================================
+ Hits         5236     5238       +2     
+ Misses        228      227       -1     

Files Changed	Coverage Δ
...cution-environments/src/common/BaseSnapExecutor.ts	89.18% <100.00%> (+0.75%)	⬆️

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