tests: Ensure profiler_type is defined in all tests

See my description in [this](https://github.com/Granulate/gprofiler/pull/451/files#r975877845) comment, specifically point 3. Tests are hardcoding the profiler type, but in some cases, the infra needs to know which profiler is going to be used, because it affects the way we will run the profiled application (the case is `nodejs` where depending on the profiler we will run the process with different flags).
If all tests were to define it properly, we could just use the `profiler_type` fixture.