packaging: remove pyoxidizer.bzl from packaging directory
We have another version in rust/hgcli that is more modern
and is already associated with our Rust CLI project.
Differential Revision: https://phab.mercurial-scm.org/D8471
contrib: install PyOxidizer in Linux and Windows environments
For Linux, this was trivial.
For Windows, we need to teach the powershell script to install
Rust as well. This was also pretty straightforward.
Differential Revision: https://phab.mercurial-scm.org/D8468