Introduce test types in metadata

[acerv]

We would like to remove runtest files as they are prone to failure during maintenance. The idea is to provide a struct tst_test -> type that can be used to filter out tests which are testing specific subsystems. This should be done, for example, via kirk (but not only) command in the following way:

kirk --run-by-rule "type=syscalls AND type=memory"

[metan-ucw]

I would call it group rather than type but that is very minor.

The groups would either be explicitly added to a testcase with:

struct tst_test tst_test = {
        ...
        .groups = {"foo", "bar", NULL},
       ...
}

Or auto-generated during the metadata creation, couple of ways how to auto-generate the groups:

• Anything that has CVE tag will be part of cve group
• Anything under syscall directory will be syscalls group
• sysvipc group will be any tests in syscall group whose filename matches sysvipc syscall
• ...

Once that is done and once the variants are in we can pretty much generate the runtest files on the fly.