group codegen test files into directories per test case

idea/testData/codegen/controlStructures/while.jet

@@ -0,0 +1,9 @@
+fun fac(i: Int): Int {
+    var count = 1;
+    var result = 1;
+    while(count < i) {
+        count = count + 1;
+        result = result * count;
+    }
+    return result;
+}