Adds run.log_stream to take over from run.low_raw
    
    `log_raw` is mixing together two use cases: provides access to a plain-test
    version fo the log, and can be used to read output of the process in the
    real-time. `log_raw` can point to the external storage used while
    `log_stream` is tied with the system running the test and may very well
    be necessarily set to a completely different value. Therefore the
    extra field, not mixing these two together - the fact that `log_raw` and
    `log_stream` *can* have the same value for some time is an
    implementation detail, an accident.