Use the same version of Debian for all of the cleanup containers

### Problem Statement

To build `sentry-cleanup`, `snuba-cleanup`, `snuba-transactions-cleanup` and `symbolicator-cleanup`, I need to use an HTTPS proxy of my company (for the APT repository) to execute `apt-get update && apt-get install -y --no-install-recommends cron` (https://github.com/getsentry/onpremise/blob/21.10.0/cron/Dockerfile).

Sentry, Snuba et Symbolicator are using different versions of Debian:
* https://github.com/getsentry/snuba/blob/master/Dockerfile => Debian 11 Bullseye
* https://github.com/getsentry/sentry/blob/master/docker/Dockerfile => Debian 10 Buster
* https://github.com/getsentry/symbolicator/blob/master/Dockerfile => Debian 9 Stretch

I need to set a different `sources.list` file for those three. And it's especially troublesome with Symbolicator because Debian 9 Stretch doesn't have [apt-transport-https](https://packages.debian.org/search?keywords=apt-transport-https) installed. (see [this PR](https://github.com/getsentry/symbolicator/pull/356))

### Solution Brainstorm

Can all the containers use the same version of Debian (Buster or Bullseye) to ease their personalization? Or can they embed `cron` natively so the Dockerfile builds to install `cron` become unneeded?

### Todo

- [ ] symbolicator - https://github.com/getsentry/symbolicator/pull/578
- [ ] sentry - https://github.com/getsentry/sentry/pull/29946