Test or descriptor level timeout configuration option

[pranavparikh]

Currently Arrow supports the --testTimeOut parameter, but this is global across
all descriptors. We have a few tests which take longer to run, but we don't
want to increase the global time out, as this would cause full failures to take
much longer to fail.

Ideally, we could have a JSON configuration option for the default controller
that could change this value to suit the specific case. Alternatively, setting
it in the descriptor config would get us most of the way, if that's more
convenient.