rename: show conflict if renamed method erased signature would conflict with existing method (IDEA-111875)

java/java-tests/testData/refactoring/renameCollisions/RenameMethodCollisionSameSignature.java

@@ -0,0 +1,7 @@
+class RenameTest<T> {
+    void f<caret>oo(T t) {
+    }
+
+    void foo1(Object t) {
+    }
+}