twister: rework how we discard tests

Add a filter type to distinguish between testsuite filters that are
maintained in the testcase.yaml file and those provided on the command
line.

The issue was that when something is excluded deliberately on the command
line twister would report an error if that filter would filter out an
integration platform. We do not want that, because the filtering is
being done by the caller knowing that some tests would be not run, even
if those are integration platforms.

Signed-off-by: Anas Nashif <anas.nashif@intel.com>