Add the tests/sys/arch directory for architecture-specific tests and
use it to add arm64 SVE tests. These test the kernel is managing the
SVE state in a way we expect.
These tests require SVE hardware support to run so will skip when they
can't detect it.
Reviewed by: markj
Sponsored by: Arm Ltd
Differential Revision: https://reviews.freebsd.org/D43311
Andrew Turner
0ddaa4c86d