Revert [JS IR] commits that failed build

Revert "[JS IR] Build hybrid versions of stdlib and kotlin.test"
This reverts commit b9f88350dd.

Revert "[JS IR] Add gradle plugin integration tests"
This reverts commit d872b27663.

Revert "Update bootstrap"
This reverts commit bc47594c7a.

Revert "[JS IR] Support generating both IR and pre-IR libraries"
This reverts commit 1b8df45bfe.

libraries/tools/kotlin-maven-plugin/src/main/java/org/jetbrains/kotlin/maven/K2JSCompilerMojo.java

@@ -105,9 +105,8 @@ public class K2JSCompilerMojo extends KotlinCompileMojoBase<K2JSCompilerArgument
         arguments.setMetaInfo(metaInfo);
         arguments.setModuleKind(moduleKind);
         arguments.setMain(main);
-        arguments.setIrOnly(useIrBackend);
-        arguments.setIrProduceJs(useIrBackend);
-        arguments.setIrProduceKlibDir(useIrBackend);
+        arguments.setIrBackend(useIrBackend);
+        arguments.setIrLegacyGradlePluginCompatibility(true);
 
         List<String> libraries;
         try {