Forbid splitting getter/setter across classes

This horrible code:

private #foo;
class ReturnOverride {
  constructor() {
    return {
      get outer #foo() {}
    };
  }
}
class AddSetter extends ReturnOverride {
  set outer #foo(x) {}
}
new AddSetter;

or

class ReturnOverride {
  get #foo () {}
  
  static AddSetter = class extends ReturnOverride {
    set outer #foo(x) {}
  };
}
new ReturnOverride.AddSetter;

should not be legal (at runtime). I expect this will happen naturally in the spec but need to be sure (and have tests).

No files or tests are named. Start by reading the proposal's runtime semantics around private getter/setter declarations, then check both examples in the issue. Done means the split getter/setter cases are rejected at runtime and tests cover both forms.