Get rid of 'class object' usages in code and builtins

Replace some comments and library usages as well

libraries/examples/kotlin-gradle-subplugin-example/src/main/kotlin/example/CompilerPlugin.kt

@@ -31,7 +31,7 @@ public object ExampleConfigurationKeys {
 }
 
 public class ExampleCommandLineProcessor : CommandLineProcessor {
-    class object {
+    companion object {
         public val EXAMPLE_PLUGIN_ID: String = "example.plugin"
         public val EXAMPLE_OPTION: CliOption = CliOption("exampleKey", "<value>", "")
     }

libraries/stdlib/src/kotlin/concurrent/FunctionalList.kt

@@ -48,7 +48,7 @@ public abstract class FunctionalList<T>(public val size: Int) {
 
     private class Standard<T>(override val head: T, override val tail: FunctionalList<T>) : FunctionalList<T>(tail.size + 1)
 
-    class object {
+    companion object {
         public fun <T> emptyList(): FunctionalList<T> = Empty<T>()
 
         public fun <T> of(element: T): FunctionalList<T> = FunctionalList.Standard<T>(element, emptyList())

libraries/tools/kotlin-js-tests-junit/src/test/kotlin/tests/SeleniumTestSuite.kt

@@ -14,7 +14,7 @@ public class SeleniumTest(val id: String) {
         println("Testing $id")
     }
 
-    class object {
+    companion object {
         Parameters public fun findSeleniumUris(): List<String> {
             return arrayList("a", "b")
         }

libraries/tools/kotlin-stdlib-gen/src/generators/GenerateJavaScriptStubs.kt

@@ -150,7 +150,7 @@ $imports
             if (fields != null) {
                 if (fields.isNotEmpty()) {
                     println("")
-                    println("    public class object {")
+                    println("    public companion object {")
                     for (field in fields) {
                         if (field != null) {
                             val modifiers = field.getModifiers()