linux-base: add linux-sysctl-defaults package like in Debian

[Luca Boccassi]

Debian recently added a new binary arch: all package in linux-base, linux-sysctl-defaults. This package allows the kernel team to control the default sysctl options (imported from the systemd repository) applied on the system, both in full images and in kernel-less container images (hence why it is separate from src:linux).
I want to add a dependency from systemd to this package, but it would break the upstream CI as Ubuntu currently does not ship it. Please consider shipping it, like Debian does, with the same name.

https://packages.debian.org/unstable/linux-sysctl-defaults

https://salsa.debian.org/kernel-team/linux-base/-/commit/9222e39beb2666c19b0ed4f056803b3100fce42d

https://salsa.debian.org/kernel-team/linux-base/-/commit/0863535f2bbd5eda93c0d7a6b52f9ea46f173aef