twister: add details on a depends_on filter hit

In situations where a test won't be run because there is a gap
in the hardware support, add the gap information to the "reason"
field to aid in debugging test cases.

With this change, the reason field for the error in test case
will show the gap:

e.g. reason field now updated with gaps

"No hardware support {'usbd'} but is one of the integration platforms"

Signed-off-by: David Leach <david.leach@nxp.com>