[listen] improve onError API

[chunhtai]

flutter/flutter treats different error differently.

For stateError when using changenotifier, it throws synchronously

for Error raise during listener callback, it uses reportError and continue execution.

Improve the Error API so that framework can tell where the error is raised

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[gemini-code-assist]

Code Review

This pull request updates ErrorCallback to pass the raw error object and original StackTrace, and introduces an optional ErrorContext parameter to distinguish listener errors from assertion errors. The default onError implementation is updated to rethrow errors preserving their stack trace. Review feedback suggests fallback logic to preserve the stack trace of Error objects when the provided stack trace is null, and recommends using list assertions in tests instead of .single to improve test failure diagnostics.

[gemini-code-assist]

When stackTrace is null, we can try to preserve the original stack trace of the error if it is an Error object (which has a stackTrace getter) before falling back to StackTrace.current. This helps preserve the original context of where the error was created.

  static ErrorCallback onError = (\n    Object error,\n    StackTrace? stackTrace, {\n    ErrorContext? context,\n  }) {\n    Error.throwWithStackTrace(\n      error,\n      stackTrace ?? (error is Error ? error.stackTrace : null) ?? StackTrace.current,\n    );\n  };