Ladybird: Render web content in a separate process :^)

This patch brings over the WebContent process over from SerenityOS
to Ladybird, along with a new WebContentView widget that renders
web content in a separate process.

There's a lot of jank and FIXME material here, notably I had to re-add
manually pumped Core::EventLoop instances on both sides, in order to get
the IPC protocol running. This introduces a lot of latency and we should
work towards replacing those loops with improved abstractions.

The WebContent process is built separately here (not part of Lagom) and
we provide our own main.cpp for it. Like everything, this can be better
architected, it's just a starting point. :^)

Ladybird/CMakeLists.txt

@@ -50,32 +50,26 @@ find_package(Qt6 REQUIRED COMPONENTS Core Widgets Network)
 
 set(SOURCES
     BrowserWindow.cpp
-    ConsoleClient.cpp
-    ConsoleGlobalObject.cpp
     CookieJar.cpp
-    EventLoopPluginQt.cpp
-    FontPluginQt.cpp
-    ImageCodecPluginLadybird.cpp
-    ModelTranslator.cpp
-    PageClientLadybird.cpp
-    RequestManagerQt.cpp
-    main.cpp
+    WebContentView.cpp
     History.cpp
+    ModelTranslator.cpp
     Settings.cpp
     SettingsDialog.cpp
-    SimpleWebView.cpp
     Tab.cpp
-    TimerQt.cpp
     Utilities.cpp
-    WebSocketClientManagerLadybird.cpp
-    WebSocketLadybird.cpp
+    main.cpp
 )
 
 qt_add_executable(ladybird ${SOURCES}
     MANUAL_FINALIZATION
 )
+#target_link_libraries(ladybird PRIVATE Qt::Widgets Qt::Network LibWeb LibGUI LibWeb LibWebView LibGL LibSoftGPU LibMain)
 target_link_libraries(ladybird PRIVATE Qt::Widgets Qt::Network LibWeb LibWebSocket LibGUI LibWebView LibGL LibSoftGPU LibMain)
 
+target_include_directories(ladybird PRIVATE ${CMAKE_CURRENT_BINARY_DIR})
+target_include_directories(ladybird PRIVATE ${SERENITY_SOURCE_DIR}/Userland/Services/)
+
 set_target_properties(ladybird PROPERTIES
     MACOSX_BUNDLE_GUI_IDENTIFIER org.serenityos.ladybird
     MACOSX_BUNDLE_BUNDLE_VERSION ${PROJECT_VERSION}
@@ -104,3 +98,5 @@ qt_finalize_executable(ladybird)
 if(NOT CMAKE_SKIP_INSTALL_RULES)
     include(cmake/InstallRules.cmake)
 endif()
+
+add_subdirectory(WebContent)