Ladybird: Abstract spawning helper processes into separate methods

This will let us use the same path discovery methods for WebContent,
SQLServer, and any other helper processes we need to launch.

Ladybird/HelperProcess.h

@@ -0,0 +1,18 @@
+/*
+ * Copyright (c) 2023, Andrew Kaster <akaster@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#define AK_DONT_REPLACE_STD
+
+#include <AK/Error.h>
+#include <AK/Optional.h>
+#include <AK/Span.h>
+#include <AK/StringView.h>
+#include <LibCore/System.h>
+
+ErrorOr<void> spawn_helper_process(StringView process_name, Span<StringView> arguments, Core::System::SearchInPath, Optional<Span<StringView>> environment = {});
+ErrorOr<Vector<String>> get_paths_for_helper_process(StringView process_name);