Reduce use of unsafe code

[DemiMarie]

We currently use unsafe rust code in various places. Much of it is for FFI and can’t be helped, but some of it can be eliminated, or moved into a separate crate.

[dralley]

Can the FFI be transferred to https://github.com/rpm-software-management/librpm.rs?

[DemiMarie]

Much of it can be, yes. At a minimum both could share an autogenerated rpm-sys crate. rpm-oxide does need to support Qubes OS’s dom0 (which runs Fedora 32) and Debian stable without outside dependencies as it is used in production on both distributions.