Update `StackOverflowError.stackTrace` documentation

[sgrekhov]

The current StackOverflowError.stackTrace documentation reads:

The stack trace at the point where this error was first thrown.

Classes which extend Error will automatically have a stack trace filled in the first time they are thrown by a throw expression.

In fact, this property is always null for this class. See https://github.com/dart-lang/sdk/issues/28179 Looks like this documentation is a simply copy/paste from Error.stackTrace. Need to update it and reflect the fact that for the class StackOverflowError this property is always null.

P.S. "Classes which extend Error will automatically have a stack trace filled...". Dart API has no classes which extend Error, only bunch of classes which implements Error

[lrhn]

That's the wonder of inherited documentation. It's correct for Error itself, but subclasses that don't extend Error may want to change documentation.

The Dart API do have classes extending Error: AssertionError, ArgumentError, IndexError, NoSuchMethodError, RangeError, StateError, TypeError and UnimplementedError at least. (Every error defined in errors.dart except for StackOverflowError and OutOfMemoryError.)

[sgrekhov]

The Dart API do have classes extending Error

Ups, sorry. I read the documentation and it contains list of 'implementers' only and doesn't have list of 'Known subclasses' like Java API does. It misleaded me.

[lrhn]

This is probably the only place where it matters whether a class extends or implements a supertype, so it's unsurprising that DartDoc doesn't make the distinction.