feat(go_indexer): overriding method type satisfies interface method type (#3635)

The type of any method seen to override an interface method will now
have a `satisfies` edge to the interface method's type.

```
type I interface {
  //- @M defines/binding MI
  //- MI typed IType
  M()
}

type S struct {}

//- @M defines/binding MS
//- MS overrides MI
//- MS typed SType
//- SType satisfies IType    <------ new edge
func (S) M() {}
```
4 files changed