If we set m_waiting_for_messages to true for the intial message request,
we might never receive a response, and block the console from requesting
any more messages indefinitely. Instead, issue a non-blocking initial
request, which is how the Qt and Serenity chromes behaved before the
ConsoleClient abstraction.
This also changes ConsoleClient::clear() to use run_javascript() rather
than js_console_input(), as that is also how the chromes used to behave.
This creates WebView::ConsoleClient to handle functionality that will be
common to the JS consoles of all Ladybird chromes. This will let each
chrome focus on just the UI.
Note that this includes the `console.group` functionality that only the
Serenity chrome previously had. This was a FIXME in the Qt chrome, and
it is implemented such that all chromes will receive this functionality
for free.
