Install Linux 5.3 from sid

We install it from experimental for 4.0~rc1, but we shouldn’t ship a kernel from experimental in 4.0.

The relevant commit is 031cf21cc898693476bad209db4815805c05aded.

Feature Branch: bugfix/17124-17161-linux-5.3-from-sid+force-all-tests

Original created by @segfault on 17124 (Redmine)

To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information