tools/testing/devsec: Add basic evidence retrieval validation

Checkout basic operation of the device-evidence netlink ABI, with the
corresponding device-evidence sample utility that handles blob reassembly.

Cc: Alexey Kardashevskiy <aik@amd.com>
Cc: Xu Yilun <yilun.xu@linux.intel.com>
Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@kernel.org>
Signed-off-by: Dan Williams <djbw@kernel.org>