split err.stack so embedded stacks in err message render once

[mostafaNazari702]

PR Checklist

• Addresses an existing open issue: fixes 🐛 Bug: Reports the Error twice when its message contains something similar to a stack #3992
• That issue was marked as status: accepting prs
• Steps in CONTRIBUTING.md were taken

Overview

getFullErrorStack used to split err.stack by searching for err.message in it. that breaks when mocha filters stack traces and rewrites file paths, message stays unchanged but the stack changes so indexOf fails and the error gets printed twice (message + full stack).

What we do now is instead of matching the message string we now parse the stack the V8 way: treat the trailing "at ......." lines as the stack frames and everything above as the message. If the stack doesn't match V8 format we fall back to the old behavior.
We also keep err.inspect() overrides and err.cause chaining working as before.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.73%. Comparing base (bf76999) to head (462e353).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5997      +/-   ##
==========================================
+ Coverage   82.64%   82.73%   +0.08%     
==========================================
  Files          62       62              
  Lines        4668     4691      +23     
  Branches     1003     1042      +39     
==========================================
+ Hits         3858     3881      +23     
  Misses        810      810              

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[JoshuaKGoldberg]

Tricky stuff 😎