Modify default timeouts

Decrease overall timeouts from 20 to 10 minutes for most modules.

But for:

• swh-web: Increase timeout to 25 min. Current 20 minutes is not enough [1]
• swh-storage: Keep a slightly larger timeout of 15 min (lots of tests with multiple backend implementations) [3]

(1] Master build history [2] shows almost half of the last master build got aborted (5 out
of 11).

[2] https://jenkins.softwareheritage.org/view/swh%20master/job/DWAPPS/job/tests/

[3] https://jenkins.softwareheritage.org/job/DSTO/job/tests/