go/types: mismatching 'indirect' results from NewMethodSet and LookupFieldOrMethod for interface methods

For `T` below, we get different results for whether or not `m` is indirect when using the NewMethodSet vs LookupFieldOrMethod APIs:

```
type T interface{ m() }
```

https://go.dev/play/p/yvswbEovSem

Unless I'm misunderstanding, these APIs should agree.

CC @griesemer 