use mixin class for cp2k

[smoors]

additional improvements to the mixin class:

• add hook set_tag_ci() to the mixin class, which is used if both bench_name_ci and bench_name are set. we could also make this a mandatory attribute, to be discussed.
• make measure_memory_usage a reframe variable that can be set on the cmd line with reframe -S measure_memory_usage=True

cp2k.py file reduced from 114 lines to 76 \o/

[casparvl]

Hm, I find this only mildly useful, since bench_name is not a standard reframe test property. I.e. essentially you replaced defining a pipeline hook after init to set the tag with two property definitions. I'm not against it, but the gain is relatively minor. It does make the child test more 'configuration-only', and less programming, that's true.

One potential issue is if someone wants to do more complex stuff, e.g. set one test case to CI for CPU runs and another for GPU runs. I mean, it's still possible, they can then define the self.bench_name_ci conditionally on the CPU vs GPU part.

The one thing this does make sure is that the tag is standardized (though we also did that by making it a constant).

Ok, I'm convinced, this is useful enough (but does need to be documented - I realize I didn't document the use of the CI tag at all in my portable-test-instructions)

[casparvl]

Looks good to me. We should adapt the docs to document the self.bench_name and self.bench_name_ci.