Ladybird: Decode images out of process

This patch brings a service to handle image decompression. With it comes
security enhancement due to the process boundary. Indeed, consequences
of a potential attack is reduced as only the decoder will crash without
perturbing the WebContent process.
It also allows us to display pages containing images that we claim to
support but still make us crash, like for not-finished-yet decoders.

As an example, we can now load https://jpegxl.info/jxl-art.html without
crashing the WebContent process.

Userland/Libraries/LibImageDecoderClient/Client.h

@@ -30,13 +30,13 @@ class Client final
     IPC_CLIENT_CONNECTION(Client, "/tmp/session/%sid/portal/image"sv);
 
 public:
+    Client(NonnullOwnPtr<Core::LocalSocket>);
+
     Optional<DecodedImage> decode_image(ReadonlyBytes, Optional<DeprecatedString> mime_type = {});
 
     Function<void()> on_death;
 
 private:
-    Client(NonnullOwnPtr<Core::LocalSocket>);
-
     virtual void die() override;
 };