Bundle dependencies

At the moment, the omnibus package is using the system packages for most of its system dependencies like `tar`, `pgdump`, etc.

We might want to bundle those inside the package as well as provide a way to override the default search mechanism in backup for those utilities.

We'll track the additions of those utilities in separate issues

The issue concerns the omnibus package, system utilities such as `tar` and `pgdump`, and Backup's utility search mechanism. No files, tests, or entry points are named, and additions are deferred to separate issues. Start by locating the package definition and utility lookup code; done would require a clearly scoped utility addition and an agreed override behavior.

Written by the indexing model from the issue text.