Move blackBoxFile() testData to box/ directory

Delete all test methods (and empty test classes), since they'll be
auto-generated

compiler/testData/codegen/box/controlStructures/kt2577.kt

@@ -0,0 +1,12 @@
+fun foo(): Int {
+    try {
+    } finally {
+        try {
+            return 1
+        } catch (e: Throwable) {
+            return 2
+        }
+    }
+}
+
+fun box() = if (foo() == 1) "OK" else "Fail"