LibJS+WebContent+Browser+js: Implement console.group() methods

This implements:
- console.group()
- console.groupCollapsed()
- console.groupEnd()

In the Browser, we use `<details>` for the groups, which is not actually
implemented yet, so groups are always open.

In the REPL, groups are non-interactive, but still indent any output.
This looks weird since the console prompt and return values remain on
the far left, but this matches what Node does so it's probably fine. :^)
I expect `console.group()` is not used much outside of browsers.

Userland/Services/WebContent/WebContentConsoleClient.h

@@ -25,7 +25,7 @@ public:
 
 private:
     virtual void clear() override;
-    virtual JS::ThrowCompletionOr<JS::Value> printer(JS::Console::LogLevel log_level, Variant<Vector<JS::Value>, JS::Console::Trace>) override;
+    virtual JS::ThrowCompletionOr<JS::Value> printer(JS::Console::LogLevel log_level, PrinterArguments) override;
 
     ClientConnection& m_client;
     WeakPtr<JS::Interpreter> m_interpreter;
@@ -33,14 +33,19 @@ private:
 
     void clear_output();
     void print_html(String const& line);
+    void begin_group(String const& label, bool start_expanded);
+    virtual void end_group() override;
 
     struct ConsoleOutput {
         enum class Type {
             HTML,
-            Clear
+            Clear,
+            BeginGroup,
+            BeginGroupCollapsed,
+            EndGroup,
         };
         Type type;
-        String html;
+        String data;
     };
     Vector<ConsoleOutput> m_message_log;
 };