[FIR] Type "top-level classifier names in package" as Name

- This is more consistent with "top-level callable names in package" and
  simplifies the set construction quite a bit, as we can avoid a lot of
  `asString` conversions.

compiler/fir/entrypoint/src/org/jetbrains/kotlin/fir/session/NativeForwardDeclarationsSymbolProvider.kt

@@ -62,11 +62,11 @@ class NativeForwardDeclarationsSymbolProvider(
         }
     }
 
-    private val includedForwardDeclarationsByPackage: Map<FqName, Set<String>> by lazy {
-        buildMap<FqName, MutableSet<String>> {
+    private val includedForwardDeclarationsByPackage: Map<FqName, Set<Name>> by lazy {
+        buildMap<FqName, MutableSet<Name>> {
             for (classId in includedForwardDeclarations) {
                 getOrPut(classId.packageFqName) { mutableSetOf() }
-                    .add(classId.shortClassName.asString())
+                    .add(classId.shortClassName)
             }
         }
     }
@@ -157,7 +157,7 @@ class NativeForwardDeclarationsSymbolProvider(
     }
 
     override val symbolNamesProvider: FirSymbolNamesProvider = object : FirSymbolNamesProviderWithoutCallables() {
-        override fun getTopLevelClassifierNamesInPackage(packageFqName: FqName): Set<String> =
+        override fun getTopLevelClassifierNamesInPackage(packageFqName: FqName): Set<Name> =
             includedForwardDeclarationsByPackage[packageFqName].orEmpty()
     }
 }