K2: add package FQ name to ClassId of anonymous objects

This is needed because in order to figure out which declarations are
visible from anonymous objects in terms of overridability (see
`FirVisibilityChecker.isVisibleForOverriding`), we need to get the
package name of that anonymous object, because there's package-private
visibility on JVM.

 #KT-62017 Fixed

core/compiler.common/src/org/jetbrains/kotlin/name/SpecialNames.kt

@@ -37,6 +37,9 @@ object SpecialNames {
     @JvmField
     val ANONYMOUS = Name.special(ANONYMOUS_STRING)
 
+    @JvmField
+    val ANONYMOUS_FQ_NAME = FqName.topLevel(Name.special(ANONYMOUS_STRING))
+
     @JvmField
     val UNARY = Name.special("<unary>")