v2020: gitlab-ci: Increase the timeouts for the bigger jobs

Bump the timeout from 1h to 3h for the larger jobs, that is the ones related to the sdk, basesdk, devroot and sysroot ospacks/images.

They were taking more than 50 minutes and any slowdown due to any reason would likely cause them to fail, so increasing the timeout slightly is arguably a nice thing to do.

However, in the past few days we've been consistently hitting the timeouts for no clear reason, with the sdk ospacks taking a bit more than 1h30m and the sdk images taking more than 2h, so let's bump the timeout considerably until we find the issue.

This is a backport of !251 (closed) to the v2020 branch.