Minor: move callable reference IR tests to a separate directory

compiler/testData/ir/irText/expressions/callableReferences/genericMember.kt

@@ -0,0 +1,7 @@
+class A<T> {
+    fun foo() {}
+    val bar = 42
+}
+
+val test1 = A<String>::foo
+val test2 = A<String>::bar