BuildStream fails to timeout in network activities

This is starting to become a common theme, and even though it may be a bit costly, we should address it.

Ideally we should have a user configuration somewhere close to network-retries, and use it to apply a timeout in any network related activity; this could be a convention for Source implementations to honor.

Today I see that gnome7 has been sleeping on a bst track command for a very long time:

13696 ?        S      0:00  \_ /usr/sbin/CRON -f
13700 ?        Ss     0:00  |   \_ /bin/sh -c /home/builder/jhbuild2bst/autoconvert/launch-autotrack.sh
13701 ?        S      0:00  |       \_ /bin/bash /home/builder/jhbuild2bst/autoconvert/launch-autotrack.sh
24832 ?        SN     0:00  |           \_ /bin/bash /home/builder/jhbuild2bst/autoconvert/autoconvert.sh --jhbuild2bst /home/builder/jhbuild2bst --modulesets /home/builder/gnome-modulesets --source upstr
26799 ?        RN   1015:16  |               \_ /usr/bin/python3 /usr/local/bin/bst --arch aarch64 --on-error continue track --deps all core.bst --except base.bst

stracing the process tells me it's not doing anything.