[FIR] Get rid of FirSymbolProvider.getClassNamesInPackage

There was one non-removable usage of those function in FirJavaElementFinder
  and three non-trivial implementation
- `FirProvider.SymbolProvider`
- `KotlinDeserializedJvmSymbolsProvider`
- `FirBuiltinSymbolProvider`

First implementation was moved to `FirProvider` and other two was
  deleted, because in FirJavaElementFinder we need lookup only in
  classes from source code, so such methods in library providers are
  useless

#KT-41048

compiler/fir/java/src/org/jetbrains/kotlin/fir/java/FirJavaElementFinder.kt

@@ -43,13 +43,12 @@ class FirJavaElementFinder(
     private val firProvider = session.firProvider
 
     override fun findPackage(qualifiedName: String): PsiPackage? {
-        if (firProvider.symbolProvider.getClassNamesInPackage(FqName(qualifiedName)).isEmpty()) return null
+        if (firProvider.symbolProvider.getPackage(FqName(qualifiedName)) == null) return null
         return PsiPackageImpl(psiManager, qualifiedName)
     }
 
     override fun getClasses(psiPackage: PsiPackage, scope: GlobalSearchScope): Array<PsiClass> {
-        return firProvider.symbolProvider
-            .getClassNamesInPackage(FqName(psiPackage.qualifiedName))
+        return firProvider.getClassNamesInPackage(FqName(psiPackage.qualifiedName))
             .mapNotNull { findClass(psiPackage.qualifiedName + "." + it.identifier, scope) }
             .toTypedArray()
     }

compiler/fir/java/src/org/jetbrains/kotlin/fir/java/deserialization/KotlinDeserializedJvmSymbolsProvider.kt

@@ -408,11 +408,6 @@ class KotlinDeserializedJvmSymbolsProvider(
         }
     }
 
-    override fun getClassNamesInPackage(fqName: FqName): Set<Name> =
-        javaClassFinder.findPackage(fqName)
-            ?.getClasses { true }.orEmpty()
-            .mapTo(sortedSetOf(), JavaClass::name)
-
     private fun findRegularClass(classId: ClassId): FirRegularClass? =
         getClassLikeSymbolByFqName(classId)?.fir as? FirRegularClass