Complete "[IMPORTANT feature request] Support input_device_display_name_alt variables"

[davidhedlund]

Implement input_device_display_name_alt1 to input_device_display_name_alt8

This is important because otherwise it will be very difficult for people to distinguish controllers if multiple controllers are connected simultaneously .

Example: https://github.com/libretro/retroarch-joypad-autoconfig/pull/1168/files

input_device = "Sony Interactive Entertainment Wireless Controller"
input_device_display_name = "Sony Interactive Entertainment Wireless Controller (DualShock 4 v2)"
input_driver = "udev"
input_vendor_id = "1356"
input_product_id = "2508"
input_device_alt1 = "Sony Computer Entertainment Wireless Controller"
input_device_display_name_alt1 = "Sony Computer Entertainment Wireless  (DualShock 4 v1)"
input_vendor_id_alt1 = "1356"
input_product_id_alt1 = "1476"

More

• See [IMPORTANT feature request]: Support multiple input_device, input_device_display_name, input_vendor_id, and input_product_id variables #16907
• Everything was solved in that issue except alternative input_device_display_name variables, Autoconfig extension with alternative name/vid/pid #16990.

@zoltanvb