Upgrade to Linux 5.2+ with the Spectre v1 swapgs mitigations in Tails 4.0~beta2

It’s now in sid.

Upgrade doc: https://tails.boum.org/contribute/Linux_kernel/

Feature Branch: bugfix/16942-spectre-v1-swapgs+force-all-tests

Related issues

• Related to #16970 (closed)
• Blocks #16209
• Blocks #16764 (closed)

Original created by @intrigeri on 16942 (Redmine)