[FIR] Add UNCHECKED_CAST

Regenerate diagnostics code

compiler/testData/diagnostics/tests/regressions/kt307.fir.kt

@@ -1,11 +0,0 @@
-// KT-307 Unresolved reference
-
-open class AL {
-    fun get(i : Int) : Any? = i
-}
-
-interface ALE<T> : <!INTERFACE_WITH_SUPERCLASS!>AL<!> {
-    fun getOrNull(index: Int, value: T) : T {
-        return get(index) as? T ?: value
-    }
-}

compiler/testData/diagnostics/tests/regressions/kt307.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 // KT-307 Unresolved reference
 
 open class AL {

compiler/testData/diagnostics/tests/regressions/kt498.fir.kt

@@ -4,5 +4,5 @@
 class IdUnavailableException() : Exception() {}
 
 fun <T : Any> T.getJavaClass() : Class<T> {
-    return ((this as Object).getClass()) as Class<T> // Some error here, because of Exception() used above. ?!!!
-}
+    return ((this as Object).getClass()) <!UNCHECKED_CAST!>as Class<T><!> // Some error here, because of Exception() used above. ?!!!
+}

compiler/testData/diagnostics/tests/regressions/kt716.fir.kt

@@ -6,7 +6,7 @@ fun <T> typeinfo() : TypeInfo<T> = null <!CAST_NEVER_SUCCEEDS!>as<!> TypeInfo<T>
 
 fun <T> TypeInfo<T>.getJavaClass() : java.lang.Class<T> {
     val t : java.lang.Object = this as java.lang.Object
-    return t.getClass() as java.lang.Class<T> // inferred type is Object but Serializable was expected
+    return t.getClass() <!UNCHECKED_CAST!>as java.lang.Class<T><!> // inferred type is Object but Serializable was expected
 }
 
 fun <T> getJavaClass() = typeinfo<T>().getJavaClass()