Remove generated codegen tests, move all testData to box/

A single test file will be generated out of box/ directory

compiler/testData/codegen/box/multiDecl/component.kt

@@ -0,0 +1,17 @@
+class S(val a: String, val b: String) {
+  fun component1() : String = a
+  fun component2() : String = b
+}
+
+fun S.component3() = ((a + b) as java.lang.String).substring(2)
+
+class Tester() {
+  fun box() : String {
+    val (o,k,ok,ok2) = S("O","K")
+    return o + k + ok + ok2
+  }
+
+  fun S.component4() = ((a + b) as java.lang.String).substring(2)
+}
+
+fun box() = Tester().box()