tests: Allow controlling which shader models, executors and compilers to run via command line.
This is a reboot of !930 (closed). I think it's useful to be able to filter shader runner tests. Especially when developing and reiterating often on some specific problem I find it much nicer to not have all the other log lines around. Of course I could just comment out the relevant runners when doing so, but given that it's a rather common occurrence I think having some more ergonomic option is not a bad idea.