don't report USELESS_CAST in case of casting to superype using 'as'

compiler/testData/diagnostics/tests/Casts.kt

@@ -9,10 +9,15 @@ fun test() : Unit {
   checkSubtype<Int>(x as Int)
   checkSubtype<Int>(y <!USELESS_CAST!>as Int<!>)
   checkSubtype<Int?>(x <!USELESS_CAST!>as Int?<!>)
-  checkSubtype<Int?>(y <!USELESS_CAST!>as Int?<!>)
+  checkSubtype<Int?>(y as Int?)
   checkSubtype<Int?>(x <!USELESS_CAST!>as? Int<!>)
   checkSubtype<Int?>(y <!USELESS_CAST!>as? Int<!>)
   checkSubtype<Int?>(x <!USELESS_CAST!>as? Int?<!>)
-  checkSubtype<Int?>(y <!USELESS_CAST!>as? Int?<!>)
+  checkSubtype<Int?>(y as? Int?)
+
+  val <!UNUSED_VARIABLE!>s<!> = "" <!USELESS_CAST!>as Any<!>
+  ("" as String?)?.length()
+  (@data("" as String?))?.length()
+  ([data]( "" as String?))?.length()
   Unit
 }

compiler/testData/diagnostics/tests/classObjects/kt3866.kt

@@ -15,6 +15,6 @@ fun bar() {
     val x = X
     x.foo()
     X.foo()
-    (X <!USELESS_CAST!>as C<!>).foo()
+    (X as C).foo()
     ((if (1<2) X else Y) <!USELESS_CAST!>as C<!>).foo()
 }

compiler/testData/diagnostics/tests/smartCasts/kt5455.kt

@@ -13,16 +13,16 @@ class B: A()
 
 fun test(a: Any?) {
     if (a is B) {
-        (a <!USELESS_CAST!>as A<!>).foo()
+        (a as A).foo()
     }
 }
 
 fun test1(a: B) {
-    (a <!USELESS_CAST!>as A?<!>)?.foo()
+    (a as A?)?.foo()
 }
 
 fun test2(b: B?) {
     if (b != null) {
-        (b <!USELESS_CAST!>as A<!>).foo()
+        (b as A).foo()
     }
 }