Missing quick-fixes on pattern destructuring

[FMorschel]

Repro:

// other.dart
class A {}

void f(A a) {
  switch (a) {
    case A(value:int other):
      break;
  }
}

// import.dart
import 'other.dart';

extension Ext on A {
  int? get value => null;
}

If the type is declared somewhere else where we can't edit (SDK or a package), then neither the Create field/Create getter fixes show up.

Missing here:

• Create extension quick-fixes
• Add import for the extension

FYI @bwilkerson @DanTup