[FIR] Mark JavaSymbolProvider.getJavaTopLevelClasses as @TestOnly

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

@@ -9,6 +9,7 @@ import com.intellij.openapi.progress.ProcessCanceledException
 import com.intellij.openapi.project.Project
 import com.intellij.psi.PsiElement
 import com.intellij.psi.search.GlobalSearchScope
+import org.jetbrains.annotations.TestOnly
 import org.jetbrains.kotlin.descriptors.ClassKind
 import org.jetbrains.kotlin.descriptors.Modality
 import org.jetbrains.kotlin.descriptors.Visibilities
@@ -16,9 +17,8 @@ import org.jetbrains.kotlin.descriptors.Visibility
 import org.jetbrains.kotlin.fir.*
 import org.jetbrains.kotlin.fir.declarations.*
 import org.jetbrains.kotlin.fir.declarations.builder.*
-import org.jetbrains.kotlin.fir.declarations.impl.FirDeclarationStatusImpl
-import org.jetbrains.kotlin.fir.expressions.builder.*
 import org.jetbrains.kotlin.fir.declarations.impl.FirResolvedDeclarationStatusImpl
+import org.jetbrains.kotlin.fir.expressions.builder.*
 import org.jetbrains.kotlin.fir.java.declarations.*
 import org.jetbrains.kotlin.fir.resolve.constructType
 import org.jetbrains.kotlin.fir.resolve.providers.AbstractFirSymbolProvider
@@ -40,8 +40,8 @@ import org.jetbrains.kotlin.name.FqName
 import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.resolve.jvm.KotlinJavaPsiFacade
 import org.jetbrains.kotlin.types.Variance.INVARIANT
-import org.jetbrains.kotlin.utils.addIfNotNull
 import org.jetbrains.kotlin.util.OperatorNameConventions
+import org.jetbrains.kotlin.utils.addIfNotNull
 
 class JavaSymbolProvider(
     val session: FirSession,
@@ -412,6 +412,7 @@ class JavaSymbolProvider(
         }
     }
 
+    @TestOnly
     fun getJavaTopLevelClasses(): List<FirRegularClass> {
         return classCache.values
             .filterIsInstance<FirRegularClassSymbol>()