[Plugins] Introduce new API for registering compiler plugins

Original `ComponentRegistrar` exposes Project to its registration method,
  so plugins should manually register extensions to it. To prepare for
  possible unbound compiler from Project API in future new  `K2ComponentRegistrar`
  introduced which provides registration method without Project at all

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

@@ -0,0 +1,65 @@
+/*
+ * 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
+
+import com.intellij.openapi.project.Project
+import org.jetbrains.annotations.TestOnly
+import org.jetbrains.kotlin.config.CompilerConfiguration
+import org.jetbrains.kotlin.config.CompilerConfigurationKey
+import org.jetbrains.kotlin.extensions.ProjectExtensionDescriptor
+
+abstract class CompilerPluginRegistrar {
+    companion object {
+        val COMPILER_PLUGIN_REGISTRARS: CompilerConfigurationKey<MutableList<CompilerPluginRegistrar>> =
+            CompilerConfigurationKey.create("Compiler plugin registrars")
+    }
+
+    abstract fun ExtensionStorage.registerExtensions(configuration: CompilerConfiguration)
+
+    class ExtensionStorage {
+        private val _registeredExtensions = mutableMapOf<ProjectExtensionDescriptor<*>, MutableList<Any>>()
+        val registeredExtensions: Map<ProjectExtensionDescriptor<*>, List<Any>>
+            get() = _registeredExtensions
+
+        fun <T : Any> ProjectExtensionDescriptor<T>.registerExtension(extension: T) {
+            _registeredExtensions.getOrPut(this, ::mutableListOf).add(extension)
+        }
+    }
+
+    abstract val supportsK2: Boolean
+}
+
+fun CompilerPluginRegistrar.ExtensionStorage.registerInProject(
+    project: Project,
+    errorMessage: (Any) -> String = { "Error while registering ${it.javaClass.name} "}
+) {
+    for ((extensionPoint, extensions) in registeredExtensions) {
+        for (extension in extensions) {
+            @Suppress("UNCHECKED_CAST")
+            try {
+                (extensionPoint as ProjectExtensionDescriptor<Any>).registerExtensionUnsafe(project, extension)
+            } catch (e: AbstractMethodError) {
+                throw IllegalStateException(errorMessage(extension), e)
+            }
+        }
+    }
+}
+
+private fun ProjectExtensionDescriptor<Any>.registerExtensionUnsafe(project: Project, extension: Any) {
+    this.registerExtension(project, extension)
+}
+
+@TestOnly
+fun registerExtensionsForTest(
+    project: Project,
+    configuration: CompilerConfiguration,
+    register: CompilerPluginRegistrar.ExtensionStorage.(CompilerConfiguration) -> Unit
+) {
+    val extensionStorage = CompilerPluginRegistrar.ExtensionStorage().apply {
+        register(configuration)
+    }
+    extensionStorage.registerInProject(project)
+}

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

@@ -17,8 +17,8 @@
 package org.jetbrains.kotlin.compiler.plugin
 
 import com.intellij.mock.MockProject
-import org.jetbrains.kotlin.config.CompilerConfigurationKey
 import org.jetbrains.kotlin.config.CompilerConfiguration
+import org.jetbrains.kotlin.config.CompilerConfigurationKey
 
 interface ComponentRegistrar {
     companion object {