fix(fetch): allow custom implementation of AbortSignal

[SukkaW]

The PR closes #1605.

A test case is added to ensure it is the DOMException being thrown, not TypeError.

cc @mcollina @KhafraDev

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.88%. Comparing base (5890e16) to head (dd0bd7e).
⚠️ Report is 1886 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1608      +/-   ##
==========================================
- Coverage   94.90%   94.88%   -0.03%     
==========================================
  Files          50       50              
  Lines        4753     4752       -1     
==========================================
- Hits         4511     4509       -2     
- Misses        242      243       +1     

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[KhafraDev]

This wasn't the correct solution; it makes us fall out of line with the spec. Instead, when parsing an AbortSignal, a strict option should have been passed instead. See

undici/lib/fetch/webidl.js

Line 282 in e46d8bf

if (opts.strict !== false && !(V instanceof i)) {

Of course the webidl interface converter could also be improved such that when passing a strict: false option, it would check the object's Symbol.toStringTag/constructor name.