Add external keyword support for UL

Fixed #KT-34923

compiler/light-classes/src/org/jetbrains/kotlin/asJava/classes/ultraLightMembersCreator.kt

@@ -20,6 +20,7 @@ import org.jetbrains.kotlin.descriptors.*
 import org.jetbrains.kotlin.descriptors.annotations.Annotated
 import org.jetbrains.kotlin.extensions.DeclarationAttributeAltererExtension
 import org.jetbrains.kotlin.lexer.KtTokens
+import org.jetbrains.kotlin.lexer.KtTokens.EXTERNAL_KEYWORD
 import org.jetbrains.kotlin.lexer.KtTokens.REIFIED_KEYWORD
 import org.jetbrains.kotlin.load.java.JvmAbi
 import org.jetbrains.kotlin.load.kotlin.TypeMappingMode
@@ -283,6 +284,7 @@ internal class UltraLightMembersCreator(
                 PsiModifier.STATIC -> forceStatic || containingClassIsNamedObject && (outerDeclaration.isJvmStatic(support) || declaration.isJvmStatic(support))
                 PsiModifier.STRICTFP -> declaration is KtFunction && declaration.hasAnnotation(STRICTFP_ANNOTATION_FQ_NAME)
                 PsiModifier.SYNCHRONIZED -> declaration is KtFunction && declaration.hasAnnotation(SYNCHRONIZED_ANNOTATION_FQ_NAME)
+                PsiModifier.NATIVE -> declaration is KtFunction && declaration.hasModifier(EXTERNAL_KEYWORD)
                 else -> false
             }
         }

compiler/testData/asJava/ultraLightClasses/simpleFunctions.kt

@@ -9,5 +9,7 @@ class Foo {
   operator fun plus(increment: Int): Foo {}
   fun String.onString(a: (Int) -> Any?): Foo {}
 
+  external fun externalFun(a: Int): String { return "" }
+
   class Inner {}
 }

compiler/testData/asJava/ultraLightFacades/simpleFunctions.kt

@@ -7,3 +7,5 @@ public fun nullableVararg(vararg o: Any?): Unit
 
 operator fun plus(increment: Int): Foo {}
 fun String.onString(a: (Int) -> Any?): Foo {}
+
+external fun externalFun(a: Int): String { return "" }