Move tests variants from runtest files into tests

[metan-ucw]

In order to eventually phase out runtest files the test variants (i.e. the different test parameters) have to be moved from rutnest files somewhere, I guest the most logical plan would be to move them into the tst_test structure.

Apart from having all the information in a single place that would mean:

• the test variants would be exported into metadata and could be used by the test runner
• the test can list all test variants (e.g. with -t parameter)
• specific test variant could be executed by a shortcut (e.g. -t 2)

The open question is how to encode these. Easiest solution would be strings with a list of command line parameters, something as:

static struct tst_test tst_test = {
...
         .test_variants = [
                "-s 1024 -p 2",
                "-s 2048 -p 4",
                ...
                NULL
         ];
...
};

The corresponding kirk issue: https://github.com/linux-test-project/kirk/issues/13

[metan-ucw]

@tbird20d FYI