Remove idea/src/META-INF/extensions/{kotlin2jvm.xml,kotlin2js.xml}

Keep the EnvironmentConfigFiles enum because its values are used in
determining whether the environment is going to be used for JVM or
non-JVM project analysis, but remove the actual files.

Drop EnvironmentConfigFiles.EMPTY and replace its only usage in
preprocessor with JVM_CONFIG_FILES: it's easier and won't affect
anything

compiler/build.gradle.kts

@@ -77,9 +77,7 @@ val jar: Jar by tasks
 jar.apply {
     from(the<JavaPluginConvention>().sourceSets.getByName("main").output)
     from("../idea/src").apply {
-        include("META-INF/extensions/common.xml",
-                "META-INF/extensions/kotlin2jvm.xml",
-                "META-INF/extensions/kotlin2js.xml")
+        include("META-INF/extensions/common.xml")
     }
 }