Tapioca does not properly attribute prepended methods

I haven't verified this yet, but @paracycle told me that if one gem defines a method, and another gem overrides that method via a prepend, the prepended method will be incorrectly written to both gem RBIs.

Example:

# in gem foo
class Foo
  def foo; end
end

# in gem bar
module Bar
  def foo; end
end

Foo.prepend(Bar)

Tapioca will write bar's foo method to foo's gem RBIs, which is fine if they have the same signature, but not great if the prepend changes the method signature.

The issue names no files or tests. Start by reproducing the foo/bar prepend example in Tapioca and trace how gem RBI ownership is attributed during RBI generation. Done means the prepended foo method is attributed only to bar's gem RBI, while foo's original method remains in foo's RBI.