Remove generated codegen tests, move all testData to box/

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

compiler/testData/codegen/box/intrinsics/longRangeWithExplicitDot.kt

@@ -0,0 +1,6 @@
+fun box(): String {
+  val l: Long = 1
+  val l2: Long = 2
+  val r = l.rangeTo(l2)
+  return if (r.start == l && r.end == l2) "OK" else "fail"
+}