[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.

analysis/low-level-api-fir/src/org/jetbrains/kotlin/analysis/low/level/api/fir/providers/LLFirCombinedJavaSymbolProvider.kt

@@ -51,7 +51,7 @@ internal class LLFirCombinedJavaSymbolProvider private constructor(
     private val classCache: NullableCaffeineCache<ClassId, FirRegularClassSymbol> = NullableCaffeineCache { it.maximumSize(2500) }
 
     override val symbolNamesProvider: FirSymbolNamesProvider = object : FirSymbolNamesProviderWithoutCallables() {
-        override fun getTopLevelClassifierNamesInPackage(packageFqName: FqName): Set<String>? = null
+        override fun getTopLevelClassifierNamesInPackage(packageFqName: FqName): Set<Name>? = null
         override fun mayHaveTopLevelClassifier(classId: ClassId): Boolean = true
     }
 

analysis/low-level-api-fir/src/org/jetbrains/kotlin/analysis/low/level/api/fir/providers/LLFirCombinedSyntheticFunctionSymbolProvider.kt

@@ -35,7 +35,7 @@ internal class LLFirCombinedSyntheticFunctionSymbolProvider private constructor(
         // `FirCompositeSymbolNamesProvider` defines `mayHaveSyntheticFunctionTypes` and `mayHaveSyntheticFunctionType` correctly, which is
         // needed for consistency should this symbol provider be part of another composite symbol provider.
         object : FirCompositeSymbolNamesProvider(providers.map { it.symbolNamesProvider }) {
-            override fun getTopLevelClassifierNamesInPackage(packageFqName: FqName): Set<String> = emptySet()
+            override fun getTopLevelClassifierNamesInPackage(packageFqName: FqName): Set<Name> = emptySet()
             override fun getPackageNamesWithTopLevelCallables(): Set<String> = emptySet()
             override fun getTopLevelCallableNamesInPackage(packageFqName: FqName): Set<Name> = emptySet()
         }

analysis/low-level-api-fir/src/org/jetbrains/kotlin/analysis/low/level/api/fir/resolve/extensions/LLFirResolveExtensionTool.kt

@@ -75,11 +75,9 @@ private class LLFirResolveExtensionToolSymbolNamesProvider(
     private val packageFilter: LLFirResolveExtensionToolPackageFilter,
     private val fileProvider: LLFirResolveExtensionsFileProvider,
 ) : FirSymbolNamesProvider() {
-    override fun getTopLevelClassifierNamesInPackage(packageFqName: FqName): Set<String> = forbidAnalysis {
+    override fun getTopLevelClassifierNamesInPackage(packageFqName: FqName): Set<Name> = forbidAnalysis {
         if (!packageFilter.packageExists(packageFqName)) return emptySet()
-        fileProvider.getFilesByPackage(packageFqName)
-            .flatMap { it.getTopLevelClassifierNames() }
-            .mapTo(mutableSetOf()) { it.asString() }
+        fileProvider.getFilesByPackage(packageFqName).flatMap { it.getTopLevelClassifierNames() }.toSet()
     }
 
     override fun getPackageNamesWithTopLevelCallables(): Set<String> = forbidAnalysis {

analysis/low-level-api-fir/src/org/jetbrains/kotlin/analysis/low/level/api/fir/util/LLFirKotlinSymbolNamesProvider.kt

@@ -25,12 +25,10 @@ internal open class LLFirKotlinSymbolNamesProvider(
     private val declarationProvider: KotlinDeclarationProvider,
     private val allowKotlinPackage: Boolean? = null,
 ) : FirSymbolNamesProvider() {
-    override fun getTopLevelClassifierNamesInPackage(packageFqName: FqName): Set<String> {
+    override fun getTopLevelClassifierNamesInPackage(packageFqName: FqName): Set<Name> {
         if (allowKotlinPackage == false && packageFqName.isKotlinPackage()) return emptySet()
 
-        return declarationProvider
-            .getTopLevelKotlinClassLikeDeclarationNamesInPackage(packageFqName)
-            .mapToSetOrEmpty { it.asString() }
+        return declarationProvider.getTopLevelKotlinClassLikeDeclarationNamesInPackage(packageFqName)
     }
 
     override fun getPackageNamesWithTopLevelCallables(): Set<String>? {