fix: fix top definitions filtering

[SirYwell]

With multiple independent interfaces declaring the same method, getTopDefinitions() returned wrong results.

The filtering was broken due to TypeAdaptor#isOverriding(m, m) == true and the wrong initialization of the method (as all methods were already added to the result).

[MartinWitt]

Do I understand that correct, that before we could only find a single top definition even if the method has multiple, and now we find all?

[SirYwell]

No, it returned all methods that were overridden, not just the top definitions. In my test case, it returned the methods from C, B, A1 and A2. Now it only returns the methods from A1 and A2, as in B and C, the method is only redefined. Basically, the whole loop at the bottom of getTopDefinitions() did not change the result anymore.