Basic class members generation.

Split testData into 'classes' and 'expressions'.

compiler/testData/ir/irText/expressions/smartCastsWithDestructuring.kt

@@ -0,0 +1,10 @@
+interface I1
+interface I2
+
+operator fun I1.component1() = 1
+operator fun I2.component2() = ""
+
+fun test(x: I1) {
+    if (x !is I2) return
+    val (c1, c2) = x
+}