[FIR] add tests on external annotations

Tests are excluded in COMPILED_JAVA mode because in this
mode external annotations are not present at all

^KT-62310

compiler/test-infrastructure/tests/org/jetbrains/kotlin/test/services/SourceFileProvider.kt

@@ -1,10 +1,11 @@
 /*
- * Copyright 2010-2020 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Copyright 2010-2023 JetBrains s.r.o. and Kotlin Programming Language contributors.
  * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
  */
 
 package org.jetbrains.kotlin.test.services
 
+import com.intellij.codeInsight.ExternalAnnotationsManager
 import com.intellij.openapi.project.Project
 import com.intellij.openapi.vfs.StandardFileSystems
 import com.intellij.psi.PsiManager
@@ -139,6 +140,9 @@ val TestFile.isMjsFile: Boolean
 val TestModule.javaFiles: List<TestFile>
     get() = files.filter { it.isJavaFile }
 
+val TestFile.isExternalAnnotation: Boolean
+    get() = name == ExternalAnnotationsManager.ANNOTATIONS_XML
+
 fun SourceFileProvider.getRealJavaFiles(module: TestModule): List<File> {
     return module.javaFiles.map { getRealFileForSourceFile(it) }
 }