Timeout ports.ubuntu.com

While running `chisel cut` operations, we very often see the following error, after which chisel exits:

`#0 50.26 error: cannot talk to archive: Get "http://ports.ubuntu.com/ubuntu-ports/dists/noble/InRelease": context deadline exceeded (Client.Timeout exceeded while awaiting headers)`

Since the timeout and the mirror are both not [configurable](https://github.com/canonical/chisel/blob/main/internal/archive/archive.go#L159) via CLI parameters, we basically have to retry until _ports.ubuntu.com_ is fast enough, which is a frustrating process as it can take multiple hours. Using another internet connection does not solve the problem.

I would appreciate if it would be possible to configure `ubuntuURL`, `ubuntuOldReleasesURL` and `ubuntuPortsURL` via optional CLI parameters or if chisel would respect the local sources configuration under `/etc/apt`