Presenter: Rearchitect on top of LibWeb

This patch replaces the bespoke rendering engine in Presenter with a
simple pipeline that turns presentations into single-page HTML files.
The HTML is then loaded into an OutOfProcessWebView.

This achieves a number of things, most importantly:
- Access to all the CSS features supported by LibWeb
- Sandboxed, multi-process rendering

The code could be simplified a lot further, but I wanted to get the new
architecture in place without changing anything about the file format.

Userland/Applications/Presenter/main.cpp

@@ -1,5 +1,6 @@
 /*
  * Copyright (c) 2022, kleines Filmröllchen <filmroellchen@serenityos.org>
+ * Copyright (c) 2023, Andreas Kling <kling@serenityos.org>
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -14,7 +15,7 @@
 
 ErrorOr<int> serenity_main(Main::Arguments arguments)
 {
-    // rpath is required to load .presenter files, unix, sendfd and recvfd are required to talk to ImageDecoder and WindowServer.
+    // rpath is required to load .presenter files, unix, sendfd and recvfd are required to talk to WindowServer and WebContent.
     TRY(Core::System::pledge("stdio rpath unix sendfd recvfd"));
 
     DeprecatedString file_to_load;