Factor out all deps except Docker

We use Docker to run Sentry in a platform-neutral way, but the installation script depends on non-Docker tools such as `bash`, `awk`, `sed`, etc., which leads to portability bugs such as https://github.com/getsentry/onpremise/issues/941. There we have a [suggestion](https://github.com/getsentry/onpremise/issues/941#issuecomment-862570423) to remove all non-Docker dependencies from the installation flow. Seems like a worthy goal to me.

### Todo

- [ ] audit for non-Docker deps
- [ ] ???