Add system information as autopkgtest test artifact

One of autopkgtest's uses is to not just collect output, but to collect arbitrary artifacts.

When a test is run, anything placed in the $AUTOPKGTEST_ARTIFACTS directory will be returned with the result. When the test is driven by debci, this results is made available to the UI.

We should export at least the following as such artifacts:

• dmesg
• amdgpu_firmware_info
• lspci -nn, -t, -vmm

This needs adaptation of the control file, as privileges are required to read dmesg.