[Kernel] Improved TUs Support

- Changed name of config option to apply_title_update to better reflect what that option does
- Mount TU package to UPDATE: partition
- Simplified UserModule::title_id()
- Splitted loading module into two parts to allow applying TUs and custom patches

src/xenia/kernel/xboxkrnl/xboxkrnl_modules.cc

@@ -97,6 +97,7 @@ dword_result_t XexLoadImage_entry(lpstring_t module_name, dword_t module_flags,
     // Not found; attempt to load as a user module.
     auto user_module = kernel_state()->LoadUserModule(module_name.value());
     if (user_module) {
+      kernel_state()->FinishLoadingUserModule(user_module);
       // Give up object ownership, this reference will be released by the last
       // XexUnloadImage call
       auto user_module_raw = user_module.release();