Remove generated codegen tests, move all testData to box/

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

compiler/testData/codegen/box/operatorConventions/compareTo/extensionObject.kt

@@ -0,0 +1,14 @@
+class A(val x: Int)
+
+fun A.compareTo(other: A) = x.compareTo(other.x)
+
+fun checkLess(x: A, y: A) = when {
+    x >= y    -> "Fail $x >= $y"
+    !(x < y)  -> "Fail !($x < $y)"
+    !(x <= y) -> "Fail !($x <= $y)"
+    x > y     -> "Fail $x > $y"
+    x.compareTo(y) >= 0 -> "Fail $x.compareTo($y) >= 0"
+    else -> "OK"
+}
+
+fun box() = checkLess(A(0), A(1))