selftests/hid: Add initial hidraw tests skeleton

selftests/hid: Add initial hidraw tests skeleton

Largely inspired from hid_bpf.c for the fixture setup.

Create a couple of tests for hidraw:
- create a uhid device and check if the fixture is working properly
- inject one uhid event and read it through hidraw

These tests are not that useful for now, but will be once we start adding
the ioctl and BPFs to revoke the hidraw node.

Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>
Link: https://patch.msgid.link/20240827-hidraw-revoke-v5-3-d004a7451aea@kernel.org
Signed-off-by: Benjamin Tissoires <bentiss@kernel.org>