cards can have multiple logical channels; each logical channel
has its own state of what is the current selected file + application.
Let's split the RuntimeState class into the global RuntimeState and the
per-lchan-specific RuntimeLchan class.
This code doesn't actually introduce any code that uses lchans other
than the basic logical channel (0), but just modifies the data model
to accomodate those in the future.
This information is mandatory for linear files as per TS 102 221 V15
section 126.96.36.199.3. This might not have been spotted earlier because
cards of type sysmoISIM-SJA2 accept creation without it as well.