psi2ir: dynamic array element get/set

compiler/testData/ir/irJsText/dynamic/dynamicArrayAssignment.kt

@@ -0,0 +1,7 @@
+fun testArrayAssignment(d: dynamic) {
+    d["KEY"] = 1
+}
+
+fun testArrayAssignmentFake(d: dynamic) {
+    d.set("KEY", 2)
+}