This makes the device ID assigning code common to all backends, by
moving it to AddDevice() instead of copy-pasting or replicating
the logic in the backends.
Also, to prepare for hotplugging, instead of relying on a name usage
count, the new ID assigning system always starts from ID 0 and tries
to assign the first ID that is not used.
Previously, the devices vector would be passed to all backends. They
would then manually push_back to it to add new devices. This was fine
but caused issues when trying to add synchronisation.
Instead, backends now call AddDevice() to fill m_devices so that it is
not accessible from the outside.
Disclaimer: I can't test if this works on xbox one controllers, i don't have one. But i have conformed that this UpdateMotors() is related to rumble for emulated wiimotes.
This partially reverts commit "XInput: Apply immediately as well" (1958a10b6f) from pr # https://github.com/dolphin-emu/dolphin/pull/1560
Hopefully this fixes the xbox one controller rumble issue:
https://bugs.dolphin-emu.org/issues/9071
And in theory it might reduce the used usb bandwidth, as it was originally intended before pr 1560.
@JMC47: Please do a good amount of testing, to see if this breaks rumble for wiimotes or gamecube controllers emulated with xinput devices.