Add diagnostics for get/set methods of property delegate

compiler/testData/diagnostics/tests/delegatedProperty/genericGetter.kt

@@ -0,0 +1,9 @@
+val a: Int by A(1)
+
+class A<T: Any>(i: T) {
+  fun get(t: Any?, p: String): T {
+    t.equals(p) // to avoid UNUSED_PARAMETER warning
+    throw Exception()
+  }
+}
+