Iteration 1: Backport support for unlocking VeraCrypt partitions to udisks in Stretch

Development repository: https://github.com/segfault3/udisks-debian (based on Debian’s udisks2 packaging repository: https://anonscm.debian.org/git/pkg-utopia/udisks2.git)
Branch: 2.1.8-support-tcrypt

The current udisks version (and the one in Buster) uses libblockdev to handle unlocking of block devices. The version in Stretch does not, so we will have to create an additional patch for udisks in Stretch, in order to be able to ship this functionality in Tails 3.9.

Parent Task: #15214 (closed)

Related issues

Blocks #15522 (closed)

Original created by @segfault on 15253 (Redmine)

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