Revise Regex usage in TrimStackTrace

[Youssef1313]

testfx/src/Adapter/MSTest.TestAdapter/Execution/ExceptionHelper.cs

Line 109 in beb890d

string[] stackFrames = Regex.Split(stackTrace, Environment.NewLine);

It doesn't make much sense to me to use Regex here.

Not so much allocations but would be good to reduce:

[Youssef1313]

This can even be more efficient than string.Split.

We can do the loop ourselves and use spans to not allocate anything here.

[nohwnd]

Agree. Probably was used because it has overload that takes string, rather than having to wrap the string into array to call string.split.