kernel/process: Make data member variables private

Makes the public interface consistent in terms of how accesses are done
on a process object. It also makes it slightly nicer to reason about the
logic of the process class, as we don't want to expose everything to
external code.

src/core/hle/service/fatal/fatal.cpp

@@ -51,7 +51,7 @@ enum class FatalType : u32 {
 };
 
 static void GenerateErrorReport(ResultCode error_code, const FatalInfo& info) {
-    const auto title_id = Core::CurrentProcess()->program_id;
+    const auto title_id = Core::CurrentProcess()->GetTitleID();
     std::string crash_report =
         fmt::format("Yuzu {}-{} crash report\n"
                     "Title ID:                        {:016x}\n"