fix: Attach error handler to RPC stream

[FrederikBolding]

When the execution environment fails on mobile (we still don't know the cause of this) we were seeing uncaught "Premature close" errors, which ends up crashing the app.

The issue is that all streams are destroyed when the Snap terminates (as it does if it cannot initialize). Most streams already have error handling setup via pipeline and if the Snap in question has already run this applies to the RPC stream too. The problem is that if the Snap never starts, the RPC stream also never has any error handlers attached, so instead it bubbles up the error.

This PR fixes that by attaching an error handler to the RPC stream after it has been created.

https://consensyssoftware.atlassian.net/browse/WPC-516

---

Note

Medium Risk
Touches snap execution stream lifecycle in AbstractExecutionService, which is central to snap RPC plumbing; while the change is small, it could affect error propagation/logging during initialization and teardown.

Overview
Prevents uncaught RPC stream errors during snap startup/termination by attaching an error listener to the JSON-RPC mux stream as soon as it’s created, filtering out expected Premature close noise while logging other failures.

Adds a regression test that simulates a failed/unreachable execution environment and asserts the request fails cleanly without throwing Premature close, and relaxes test utilities to accept any AbstractExecutionService instance for injection.

^{Written by Cursor Bugbot for commit c8458fa. This will update automatically on new commits. Configure here.}

[Mrtenz]

?

[FrederikBolding]

It doesn't need to be a NodeThreadExecutionService, it should allow any type

[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

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[codecov]

Codecov Report

❌ Patch coverage is 66.66667% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 98.55%. Comparing base (5a88d61) to head (c8458fa).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
...ntrollers/src/services/AbstractExecutionService.ts	66.66%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3898      +/-   ##
==========================================
- Coverage   98.56%   98.55%   -0.01%     
==========================================
  Files         425      425              
  Lines       12355    12358       +3     
  Branches     1934     1935       +1     
==========================================
+ Hits        12178    12180       +2     
- Misses        177      178       +1     

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