Make CI jobs interruptible by default

What does this Merge Request do?

Marks all CI jobs (except when running on master or tags) as interruptible.

Currently when working on a branch it isn't uncommon to end up with multiple verify jobs running concurrently from older (redundant) pipelines. Setting interruptible: true should allow GitLab to cancel these when a newer pipeline is created.

Merge Request checklist

• [-] Tests added for new functionality. If not, please raise Issue to follow-up.
• [-] This change is backward compatible. If not, please include steps to communicate to our users.
• [-] Documentation added/updated, if needed.
• [-] gdk doctor test added, if needed.