Expand the range of errors reported by libusb_open.

Currently, libusb_open reports LIBUSB_SUCCESS and LIBUSB_ERROR_NO_MEM. The latter is, in most cases, misleading. A failure is more likely to be permissions or a device that is in use elsewhere. Conveying the issue to the client software, and ultimately to the user gives the user the opportunity to better diagnose and remedy the problem.

Tests

1. LIBUSB_ERROR_BUSY - open the same device twice
2. LIBUSB_ERROR_NO_DEVICE - get list of devices, pause, unplug device, attempt to open the unplugged device.
3. LIBUSB_ERROR_ACCESS - get list of devices, pause, alter permissions on the device node, attempt to open a device.
4. LIBUSB_ERROR_INVALID_PARAM - pass a null device handle.
5. LIBUSB_ERROR_NO_MEM - get list of devices, pause, simulate heap full, attempt to open a device.

A program covering the above tests - included in Bugzilla - has been run against actual hardware to verify correctness.

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=291774

Update: a set of twenty one unit tests added. These can be run from kyua and do not require physical hardware.

usb_opener_atf/build $ kyua test
usb_opener:test_case_libusb20_access -> passed [0.002s]
usb_opener:test_case_libusb20_busy -> passed [0.002s]
usb_opener:test_case_libusb20_invalid -> passed [0.002s]
usb_opener:test_case_libusb20_no_device -> passed [0.002s]
usb_opener:test_case_libusb20_no_mem -> passed [0.002s]
usb_opener:test_case_libusb20_other -> passed [0.002s]
usb_opener:test_case_libusb20_success -> passed [0.002s]
usb_opener:test_case_libusb_access -> passed [0.002s]
usb_opener:test_case_libusb_busy -> passed [0.002s]
usb_opener:test_case_libusb_invalid -> passed [0.002s]
usb_opener:test_case_libusb_no_device -> passed [0.002s]
usb_opener:test_case_libusb_no_mem -> passed [0.002s]
usb_opener:test_case_libusb_other -> passed [0.002s]
usb_opener:test_case_libusb_success -> passed [0.003s]
usb_opener:test_case_libusb_with_vid_pid_access -> passed [0.002s]
usb_opener:test_case_libusb_with_vid_pid_busy -> passed [0.002s]
usb_opener:test_case_libusb_with_vid_pid_invalid -> passed [0.002s]
usb_opener:test_case_libusb_with_vid_pid_no_device -> passed [0.002s]
usb_opener:test_case_libusb_with_vid_pid_no_mem -> passed [0.002s]
usb_opener:test_case_libusb_with_vid_pid_other -> passed [0.002s]
usb_opener:test_case_libusb_with_vid_pid_success -> passed [0.002s]

Results file id is usb_opener_atf_build.20251220-103547-089277
Results saved to ~/.kyua/store/results.usb_opener_atf_build.20251220-103547-089277.db

21/21 passed (0 broken, 0 failed, 0 skipped)