Make recovery/fastbootd USB VID/PID configurable.

Vendors are assigned their own USB vendor/product IDs for products by
the USB Implementers Forum. When booting from system, these are set
by the USB gadget HAL, but recovery has its USB gadgets configured via
init.rc, so there's no good way to configure these without copy/pasting
the init.rc and having to check whether it changed in every new Android
release. Add system properties to let vendors customize the recovery
USB IDs to make this easier.


Test: `adb reboot fastboot && fastboot wait-for-device && lsusb -d 18d1:`
Change-Id: I015a4c13c956b76972785fb38d45611bed27d4f4