[K/N] Introduce ObsoleteNativeApi annotation

An opt-in annotation to mark the Kotlin/Native standard library API
that is considered obsolete and is being phased out.

kotlin-native/runtime/src/main/kotlin/kotlin/native/ObsoleteNativeApi.kt

@@ -0,0 +1,37 @@
+/*
+ * 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 kotlin.native
+
+import kotlin.annotation.AnnotationTarget.*
+
+/**
+ * This annotation marks the Kotlin/Native standard library API that is considered obsolete and is being phased out.
+ *
+ * An obsolete API is not recommended to use, and users should migrate from it.
+ * In the future the opt-in level of the annotation might be raised to [ERROR][RequiresOptIn.Level.ERROR].
+ *
+ * Any usage of a declaration annotated with `@ObsoleteNativeApi` must be accepted either by
+ * annotating that usage with the [OptIn] annotation, e.g. `@OptIn(ObsoleteNativeApi::class)`,
+ * or by using the compiler argument `-opt-in=kotlin.native.ObsoleteNativeApi`.
+ */
+@RequiresOptIn(message = "This API is obsolete and subject to removal in a future release.", level = RequiresOptIn.Level.WARNING)
+@Retention(AnnotationRetention.BINARY)
+@Target(
+        AnnotationTarget.CLASS,
+        AnnotationTarget.ANNOTATION_CLASS,
+        AnnotationTarget.PROPERTY,
+        AnnotationTarget.FIELD,
+        AnnotationTarget.LOCAL_VARIABLE,
+        AnnotationTarget.VALUE_PARAMETER,
+        AnnotationTarget.CONSTRUCTOR,
+        AnnotationTarget.FUNCTION,
+        AnnotationTarget.PROPERTY_GETTER,
+        AnnotationTarget.PROPERTY_SETTER,
+        AnnotationTarget.TYPEALIAS
+)
+@MustBeDocumented
+@SinceKotlin("1.9")
+public annotation class ObsoleteNativeApi