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/Applications/Browser/ConsoleWidget.h

@@ -33,6 +33,8 @@ private:
 
     void request_console_messages();
     void clear_output();
+    void begin_group(StringView label, bool start_expanded);
+    void end_group();
 
     RefPtr<GUI::TextBox> m_input;
     RefPtr<Web::OutOfProcessWebView> m_output_view;
@@ -40,6 +42,13 @@ private:
     i32 m_highest_notified_message_index { -1 };
     i32 m_highest_received_message_index { -1 };
     bool m_waiting_for_messages { false };
+
+    struct Group {
+        int id { 0 };
+        String label;
+    };
+    Vector<Group> m_group_stack;
+    int m_next_group_id { 1 };
 };
 
 }