Improve handling of additional UEFI settings
For UEFI test cases since about 2 years we rely on special assets that store UEFI settings, e.g. to be able to boot from an existing installation in a qcow hdd file. These assets are handled as special cases within os-autoinst as well as openQA but need to be specified by users even though they do not want to care about them. #34783 showed this is yet another problem because we wanted to prevent restarting a job when assets are missing but we found out that tests specify "…-uefi-vars.qcow2" as a "special" asset which does not even exist except for the real UEFI test cases. We should try to improve the overall situation regarding UEFI by trying to handle the UEFI assets implicitly, i.e. hide from user, but more scalable and easier to manage for users, e.g. users do not need to specify these files in any test suite.
- AC1: UEFI assets do not need to be specified on test suites or job templates explicitly
- Maybe we can just look for the corresponding "…-uefi-vars.qcow2" file whenever UEFI=1 is set in os-autoinst
- Same for openQA
- Optional: Make sure that test suites on o3 and osd do not repeat the same UEFI asset settings in multiple test suites