Fix false warning about useless cast in property and property accessor

Note that there are some other problems, for example:
`val a = if (true) 1 as Number else 2`, here we'll get useless cast

 #KT-9551 Fixed
 #KT-9645 Fixed

compiler/testData/diagnostics/tests/Casts.kt

@@ -15,7 +15,7 @@ fun test() : Unit {
   checkSubtype<Int?>(x <!USELESS_CAST!>as? Int?<!>)
   checkSubtype<Int?>(y as? Int?)
 
-  val <!UNUSED_VARIABLE!>s<!> = "" <!USELESS_CAST!>as Any<!>
+  val <!UNUSED_VARIABLE!>s<!> = "" as Any
   ("" as String?)?.length
   (data@("" as String?))?.length
   (<!WRONG_ANNOTATION_TARGET!>@MustBeDocumented()<!>( "" as String?))?.length