simpletrace: improve parsing of sys.argv; fix files never closed.

simpletrace: improve parsing of sys.argv; fix files never closed.

The arguments extracted from `sys.argv` named and unpacked to make it
clear what the arguments are and what they're used for.

The two input files were opened, but never explicitly closed. File usage
changed to use `with` statement to take care of this. At the same time,
ownership of the file-object is moved up to `run` function. Added option
to process to support file-like objects.

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Mads Ynddal <m.ynddal@samsung.com>
Message-id: 20230926103436.25700-4-mads@ynddal.dk
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>