[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

analysis/low-level-api-fir/testData/getOrBuildFir/wholeDeclaration/notNullJavaAnnotation.txt

@@ -0,0 +1,14 @@
+KT element: KtNamedFunction
+FIR element: FirSimpleFunctionImpl
+FIR source kind: KtRealSourceElementKind
+
+FIR element rendered:
+public final [ResolvedTo(BODY_RESOLVE)] fun test(): R|kotlin/String| {
+    ^test R|/ClassWithExternalAnnotatedMembers.ClassWithExternalAnnotatedMembers|().R|/ClassWithExternalAnnotatedMembers.notNullMethod|()
+}
+
+FIR FILE:
+FILE: [ResolvedTo(IMPORTS)] usage.kt
+    public final [ResolvedTo(BODY_RESOLVE)] fun test(): R|kotlin/String| {
+        ^test R|/ClassWithExternalAnnotatedMembers.ClassWithExternalAnnotatedMembers|().R|/ClassWithExternalAnnotatedMembers.notNullMethod|()
+    }