Overloaded function is preferred over an overloaded operation

```scala
def foo(s: String): Unit = <>

interface F { def foo(s: Int): Unit }

def main() = {
val b = box new F {
def foo(s) = ()
}
b.foo("hello")
// error: Wrong number of arguments to foo: expected 1 value argument, but got 2 value arguments
}
```
[Playground link](https://effekt-lang.org/playground.html?playground=S0lNU0jLz9cotlIILinKzEvXtFIIzcssUbBVsLHj4srMK0ktSktMTlVwU6hWQFLsmVcCU1nLxQWSyE3MzNPQBOqr5lJQKEvMUUgCspPyKxTyUstBuoGiCggTQAo1NIFitUCcpAcSU8pIzcnJV9LkqgUA&repl=CmhlbGxvV29ybGQoKQo%3D)

There's no way to call the `foo` operation of `b` here, which is very unfortunate.
I think that when both are present, we should prefer the operation as there's no way to write it otherwise.

This used to work, probably broken by #1250 -- shows up in the [Effekt8 community project](https://github.com/effekt-community/Effekt8).
Probably caused by Namer already resolving it badly.

EDIT: not broken by #1250, but Namer prefers functions over operations for `foo.bar` situations.