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/loader/nro.cpp

@@ -181,7 +181,7 @@ ResultStatus AppLoader_NRO::Load(Kernel::Process& process) {
     }
 
     // Load NRO
-    const VAddr base_address = process.vm_manager.GetCodeRegionBaseAddress();
+    const VAddr base_address = process.VMManager().GetCodeRegionBaseAddress();
 
     if (!LoadNro(file, base_address)) {
         return ResultStatus::ErrorLoadingNRO;