Moved tests

that are used both for codegen & diagnostics to codegen/box/diagnostics

compiler/testData/codegen/box/diagnostics/functions/tailRecursion/sum.kt

@@ -0,0 +1,10 @@
+tailRecursive fun sum(x: Long, sum: Long): Long {
+    if (x == 0.toLong()) return sum
+    return sum(x - 1, sum + x)
+}
+
+fun box() : String {
+    val sum = sum(1000000, 0)
+    if (sum != 500000500000.toLong()) return "Fail $sum"
+    return "OK"
+}