Metrics collector: Log a separate bus for USI styluses

For USI styluses, Vendor IDs are assigned by USI, and are different from
the Vendor IDs for USB devices. Therefore, to identify a device from its
VID/PID, we need to know whether it is reporting USB product/vendor IDs
or USI ones.

Here, we introduce USI as a new bus enum value for metrics purposes.
This way, we can differentiate product identifiers based on the bus
through which it is using.

Bug: 299645968
Test: atest inputflinger_tests
Change-Id: I954e5a7c3db7d1ae3d0c6906923848fe5ced84f1