InputCommon/GCAdapter: Fix offbrand "GCAdapters".

[jordan-woyak]

This makes my Nyko-branded GCAdapter work and probably others. Please test.

Note that libusb_control_transfer calls give a LIBUSB_ERROR_BUSY error within a hotplug callback so I've introduced an Event to initialize adapters in the "scanning" thread.

I'm not entirely happy with this fix but GCAdapter needs a complete rewrite. The error handling is bad. The inter-thread communication is bad. And 90% of the logic is copy-pasted to GCAdapter_Android.cpp.

This PR does not attempt to fix the Android-side of things. I can't test there.

[JMC47]

I can test GC adapter code on Android, but I don't have Nyko.

[JMC47]

This adapter here still doesn't work.

https://cdn.discordapp.com/attachments/521710974827495435/729598461900488754/unknown.png

It spams the logs with this:

17:55:603 InputCommon\GCAdapter.cpp:91 E[SI]: adapter libusb read failed: err=LIBUSB_ERROR_IO

[NikhilNarayana]

I have had two people test master and this PR with a pdobq adapter and this fix has worked for them.

Image of the adapter for reference: https://cdn.discordapp.com/attachments/363806218181017601/729876869658181702/image0.jpg

EDIT: Just had someone test with different adapter brand and it worked
https://www.amazon.com/dp/B07Q459FBQ/ref=cm_sw_r_cp_api_i_DA-aFbY54SRKB