[Gradle] Implement kotlin-gradle-plugin-annotations module

This will include Internal* and *Experimental annotations for the
Kotlin Gradle Plugin. The separate module is proposed, so that
additional modules can use those annotations without
a dependency to the full kotlin-gradle-plugin-api module
(see -idea modules)

^KT-54029 WIP

libraries/tools/kotlin-gradle-plugin-annotations/build.gradle.kts

@@ -0,0 +1,12 @@
+plugins {
+    kotlin("jvm")
+}
+
+configureKotlinCompileTasksGradleCompatibility()
+
+publish()
+standardPublicJars()
+
+dependencies {
+    compileOnly(kotlinStdlib())
+}

libraries/tools/kotlin-gradle-plugin-annotations/src/main/kotlin/org/jetbrains/kotlin/gradle/ExperimentalKotlinGradlePluginApi.kt

@@ -0,0 +1,13 @@
+/*
+ * Copyright 2010-2022 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.gradle
+
+@RequiresOptIn(
+    message = "Experimental API in the Kotlin Gradle Plugin: No stability guarantees can be provided. " +
+            "The API could get removed in the future without replacement",
+    level = RequiresOptIn.Level.WARNING
+)
+annotation class ExperimentalKotlinGradlePluginApi

libraries/tools/kotlin-gradle-plugin-annotations/src/main/kotlin/org/jetbrains/kotlin/gradle/InternalKotlinGradlePluginApi.kt

@@ -0,0 +1,12 @@
+/*
+ * Copyright 2010-2022 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.gradle
+
+@RequiresOptIn(
+    message = "This API is not intended to be used outside of JetBrains / outside the Kotlin Gradle Plugin",
+    level = RequiresOptIn.Level.ERROR
+)
+annotation class InternalKotlinGradlePluginApi