feat(shorebird_code_push): override toString in exceptions (#266)

Co-authored-by: Felix Angelov <felix@shorebird.dev>

shorebird_code_push/lib/src/shorebird_updater.dart

@@ -26,6 +26,9 @@ class ReadPatchException implements Exception {
 
   /// The human-readable error message.
   final String message;
+
+  @override
+  String toString() => '[ShorebirdUpdater] ReadPatchException: $message';
 }
 
 /// {@template update_exception}
@@ -41,6 +44,11 @@ class UpdateException implements Exception {
 
   /// The reason the update failed.
   final UpdateFailureReason reason;
+
+  @override
+  String toString() {
+    return '[ShorebirdUpdater] UpdateException: $message (${reason.name})';
+  }
 }
 
 /// Log message when the Shorebird updater is unavailable in the current