Do not load special builtin overrides from Java as synthesized

It has been done just to avoid clashes with real declarations that look
like our builtins: e.g. 'String removeAt(int index) {}' and 'String remove(int index) {}'in Java.

But synthesized members are even weaker than extensions.

Solution is just to ignore the latter declaration and treat first as effective override
of out builltin.

compiler/testData/diagnostics/testsWithStdLib/commonCollections.txt

@@ -0,0 +1,3 @@
+package
+
+public fun foo(): kotlin.Unit