* Core: pass down Core::System reference to all services
This has to be done at once due to unified interface used by HLE/LLE switcher
* apt: eliminate Core::System::GetInstance
* gpu_gsp: eliminate Core::System::GetInstance in service
* hid: eliminate Core::System::GetInstance
* nwm: eliminate Core::System::GetInstance
* err_f: eliminate Core::System::GetInstance
There were a few places where nested namespace specifiers weren't being
used where they could be within the service code. This amends that to
make the namespacing a tiny bit more compact.
The only functional change is the error handling of GSP_GPU::ReadHWRegs function. We previously didn't return error codes (not even for success). The new returns were found by reverse engineering the GSP module.
