[Compiler] Mark all entrypoints to compiler API as experimental

compiler/plugin-api/build.gradle.kts

@@ -18,3 +18,5 @@ sourceSets {
 tasks.withType<org.jetbrains.kotlin.gradle.tasks.KotlinCompile>().configureEach {
     kotlinOptions.freeCompilerArgs += "-Xjvm-default=all-compatibility"
 }
+
+optInToExperimentalCompilerApi()

compiler/plugin-api/src/org/jetbrains/kotlin/compiler/plugin/CommandLineProcessor.kt

@@ -19,6 +19,7 @@ package org.jetbrains.kotlin.compiler.plugin
 import org.jetbrains.kotlin.config.CompilerConfiguration
 import org.jetbrains.kotlin.config.CompilerConfigurationKey
 
+@ExperimentalCompilerApi
 interface CommandLineProcessor {
     val pluginId: String
     val pluginOptions: Collection<AbstractCliOption>
@@ -63,4 +64,4 @@ interface CommandLineProcessor {
 
         return this.toMutableList()
     }
-}
+}

compiler/plugin-api/src/org/jetbrains/kotlin/compiler/plugin/CompilerPluginRegistrar.kt

@@ -11,6 +11,7 @@ import org.jetbrains.kotlin.config.CompilerConfiguration
 import org.jetbrains.kotlin.config.CompilerConfigurationKey
 import org.jetbrains.kotlin.extensions.ProjectExtensionDescriptor
 
+@ExperimentalCompilerApi
 abstract class CompilerPluginRegistrar {
     companion object {
         val COMPILER_PLUGIN_REGISTRARS: CompilerConfigurationKey<MutableList<CompilerPluginRegistrar>> =

compiler/plugin-api/src/org/jetbrains/kotlin/compiler/plugin/ComponentRegistrar.kt

@@ -25,6 +25,7 @@ import org.jetbrains.kotlin.config.CompilerConfigurationKey
     replaceWith = ReplaceWith("CompilerPluginRegistrar", "org.jetbrains.kotlin.compiler.plugin.CompilerPluginRegistrar"),
     level = DeprecationLevel.WARNING
 )
+@ExperimentalCompilerApi
 interface ComponentRegistrar {
     companion object {
         @Suppress("DEPRECATION")

compiler/plugin-api/src/org/jetbrains/kotlin/compiler/plugin/ExperimentalCompilerApi.kt

@@ -0,0 +1,9 @@
+/*
+ * 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.compiler.plugin
+
+@RequiresOptIn("This API is experimental. There are no stability guarantees for it")
+annotation class ExperimentalCompilerApi