apt-fast manager support.

[Apt-fast](https://github.com/ilikenwf/apt-fast/tree/master) is a faster version of Debian APT which I use in my GitHub Action [cache-apt-pkgs](https://github.com/awalsh128/cache-apt-pkgs-action/blob/dev-v2.0/internal/pkgs/apt.go).

I played with the manager interface a bit and tried to find a way to use the existing APT manager but repoint the binary from apt to apt-fast when needed, and gave up because I didn't want to make any major changes that could cause an issue in your repo. Lazily forked and just duped the manager, which I am not happy with but needed something to use (https://github.com/awalsh128/syspkg).

Wanted to get your ideas on the best way to implement this and I could put together a PR.