Upgrade Linux to 5.3.15+

Originally created by @intrigeri on #17332 (Redmine)

• https://tracker.debian.org/news/1085156/accepted-linux-5315-1-source-into-unstable-unstable/
• https://tails.boum.org/contribute/Linux_kernel/

Feature Branch: feature/17332-linux-5.3.15-for-stable+force-all-tests

Related issues

• Blocked by #17265 (closed)