Iteration 1: Upstream unlocking VeraCrypt partitions in Disks

The freeze for GNOME 3.30 is on July 30 so this work must be submitted upstream early enough to ensure it’s merged by then.

The code lives in https://github.com/segfault3/gnome-disk-utility (branch: support-tcrypt).

Parent Task: #15214 (closed)

Related issues

• Blocked by #15220 (closed)
• Blocks #14465 (closed)

Original created by @segfault on 15221 (Redmine)