[FIR] Make FirExtensionRegistrar a proper extension point

After that commit it's allowed to register any FIR plugin using
  existing extension infrastructure (`-Xplugin` CLI argument,
  plugin.xml for IDE plugins, etc)

plugins/parcelize/parcelize-compiler/tests/org/jetbrains/kotlin/parcelize/test/runners/AbstractFirParcelizeDiagnosticTest.kt

@@ -5,7 +5,6 @@
 
 package org.jetbrains.kotlin.parcelize.test.runners
 
-import org.jetbrains.kotlin.parcelize.test.services.FirFacadeWithParcelizeExtension
 import org.jetbrains.kotlin.parcelize.test.services.ParcelizeEnvironmentConfigurator
 import org.jetbrains.kotlin.test.bind
 import org.jetbrains.kotlin.test.builders.TestConfigurationBuilder
@@ -18,7 +17,7 @@ import org.jetbrains.kotlin.test.services.fir.FirOldFrontendMetaConfigurator
 
 abstract class AbstractFirParcelizeDiagnosticTest : AbstractKotlinCompilerTest() {
     override fun TestConfigurationBuilder.configuration() {
-        baseFirDiagnosticTestConfiguration(frontendFacade = FirFacadeWithParcelizeExtension)
+        baseFirDiagnosticTestConfiguration()
 
         defaultDirectives {
             +FirDiagnosticsDirectives.ENABLE_PLUGIN_PHASES

plugins/parcelize/parcelize-compiler/tests/org/jetbrains/kotlin/parcelize/test/runners/AbstractParcelizeBoxTest.kt

@@ -17,7 +17,6 @@ import org.jetbrains.kotlin.test.backend.ir.JvmIrBackendFacade
 import org.jetbrains.kotlin.test.bind
 import org.jetbrains.kotlin.test.builders.*
 import org.jetbrains.kotlin.test.directives.CodegenTestDirectives.REQUIRES_SEPARATE_PROCESS
-import org.jetbrains.kotlin.test.directives.DiagnosticsDirectives.DIAGNOSTICS
 import org.jetbrains.kotlin.test.directives.DiagnosticsDirectives.REPORT_ONLY_EXPLICITLY_DEFINED_DEBUG_INFO
 import org.jetbrains.kotlin.test.directives.FirDiagnosticsDirectives.ENABLE_PLUGIN_PHASES
 import org.jetbrains.kotlin.test.frontend.classic.ClassicFrontend2ClassicBackendConverter
@@ -26,6 +25,7 @@ import org.jetbrains.kotlin.test.frontend.classic.ClassicFrontendFacade
 import org.jetbrains.kotlin.test.frontend.classic.ClassicFrontendOutputArtifact
 import org.jetbrains.kotlin.test.frontend.classic.handlers.ClassicDiagnosticsHandler
 import org.jetbrains.kotlin.test.frontend.fir.Fir2IrResultsConverter
+import org.jetbrains.kotlin.test.frontend.fir.FirFrontendFacade
 import org.jetbrains.kotlin.test.frontend.fir.FirOutputArtifact
 import org.jetbrains.kotlin.test.frontend.fir.handlers.FirDiagnosticsHandler
 import org.jetbrains.kotlin.test.model.*
@@ -116,7 +116,7 @@ open class AbstractParcelizeFirBoxTest : AbstractParcelizeBoxTestBase<FirOutputA
     TargetBackend.JVM_IR
 ) {
     override val frontendFacade: Constructor<FrontendFacade<FirOutputArtifact>>
-        get() = FirFacadeWithParcelizeExtension
+        get() = ::FirFrontendFacade
 
     override val frontendToBackendConverter: Constructor<Frontend2BackendConverter<FirOutputArtifact, IrBackendInput>>
         get() = ::Fir2IrResultsConverter

plugins/parcelize/parcelize-compiler/tests/org/jetbrains/kotlin/parcelize/test/services/FirFacadeWithParcelizeExtension.kt

@@ -1,16 +0,0 @@
-/*
- * Copyright 2010-2021 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.parcelize.test.services
-
-import org.jetbrains.kotlin.parcelize.fir.FirParcelizeExtensionRegistrar
-import org.jetbrains.kotlin.test.Constructor
-import org.jetbrains.kotlin.test.frontend.fir.FirFrontendFacade
-
-val FirFacadeWithParcelizeExtension: Constructor<FirFrontendFacade> = { testServices ->
-    FirFrontendFacade(testServices) {
-        it.registerExtensions(FirParcelizeExtensionRegistrar().configure())
-    }
-}

plugins/parcelize/parcelize-compiler/tests/org/jetbrains/kotlin/parcelize/test/services/ParcelizeEnvironmentConfigurator.kt

@@ -9,8 +9,10 @@ import com.intellij.openapi.project.Project
 import org.jetbrains.kotlin.backend.common.extensions.IrGenerationExtension
 import org.jetbrains.kotlin.cli.jvm.config.addJvmClasspathRoots
 import org.jetbrains.kotlin.config.CompilerConfiguration
+import org.jetbrains.kotlin.fir.extensions.FirExtensionRegistrar
 import org.jetbrains.kotlin.parcelize.ParcelizeComponentRegistrar
 import org.jetbrains.kotlin.parcelize.ParcelizeFirIrGeneratorExtension
+import org.jetbrains.kotlin.parcelize.fir.FirParcelizeExtensionRegistrar
 import org.jetbrains.kotlin.test.model.TestModule
 import org.jetbrains.kotlin.test.services.EnvironmentConfigurator
 import org.jetbrains.kotlin.test.services.TestServices
@@ -31,6 +33,7 @@ class ParcelizeEnvironmentConfigurator(
 
     override fun registerCompilerExtensions(project: Project) {
         if (useFirExtension) {
+            FirExtensionRegistrar.registerExtension(project, FirParcelizeExtensionRegistrar())
             IrGenerationExtension.registerExtension(project, ParcelizeFirIrGeneratorExtension())
         } else {
             ParcelizeComponentRegistrar.registerParcelizeComponents(project)