Configuration UI for choosing the onnx backend

[jcelerier]

• Create a new settings{model,view,presenter}. I recommend just copying the folder from https://github.com/ossia/score/tree/master/src/plugins/score-plugin-remotecontrol/RemoteControl/Settings in here, and rename those into, say ONNX Settings. https://github.com/ossia/score/blob/master/src/plugins/score-plugin-remotecontrol/score_plugin_remotecontrol.cpp#L36 to get ossia to know about them.
• Add a setting to choose the backend. Available backends depend on the platform: https://onnxruntime.ai/docs/execution-providers/
• onnxruntime_cxx_api.h has std::vector<std::string> GetAvailableProviders(); though I think it would still list nvidia even if in a computer without a nvidia gpu ? not sure.
• Add a setting to choose which GPU is / are used
• CPU by default unless we detect an nvidia card.

Should be a good starting point!