src: improve error message for invalid child stdio type in spawn_sync

[dario-piotrowicz]

This is pretty minor, but as I was looking into #52776 (which I still am) and I noticed that the current error message that users see is not super helpful:

  #  Assertion failed: "Unreachable code reached" __VA_OPT__(": ") "invalid child stdio type"

What I'm doing in here is simply updating this so that instead what the user sees the following:

invalid child stdio type: wrap

  #  <node binary location>[192863]: v8::Maybe<int> node::SyncProcessRunner::ParseStdioOption(int, v8::Local<v8::Object>) at ../src/spawn_sync.cc:1061
  #  Assertion failed: "Unreachable code reached"

(where wrap is the problematic stdio type I get for #52776)

I'm not really good at C++ (I'm still learning), so if there is a better way of doing the above I would really love
some suggestions 🙂

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 3 lines in your changes missing coverage. Please review.

Project coverage is 90.24%. Comparing base (ffc1cf6) to head (fb26425).
Report is 28 commits behind head on main.

Files with missing lines	Patch %	Lines
src/spawn_sync.cc	0.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #57589      +/-   ##
==========================================
+ Coverage   90.22%   90.24%   +0.01%     
==========================================
  Files         630      630              
  Lines      185149   185151       +2     
  Branches    36236    36241       +5     
==========================================
+ Hits       167058   167090      +32     
+ Misses      11035    11027       -8     
+ Partials     7056     7034      -22     

Files with missing lines	Coverage Δ
src/spawn_sync.cc	68.57% <0.00%> (-0.19%)	⬇️

... and 22 files with indirect coverage changes

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[anonrig]

cc @nodejs/cpp-reviewers

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/65937/