Distribute binary version that doesn't require a system python

We currently distribute opensafely-cli via pip. This is not great:

1. it requires a user to have a system python installed
2. it means we need to support a wider range of pythons (which means job-runner needs to also support the same range)
3. it requires us to vendor all our dependencies to simplify the the UX, which increases maintenance costs, and prevent any C-level dependencies.

Ideally, we would distribute opensafely-cli as a binary, which:

a) includes the specific version of python we want to use
b) includes all the dependencies at build time
c) is platform specific so we can use C dependencies

One promising avenue for this is pyoxidizer. This is a rust tool chain that builds a platform specific binary with your code, deps, and a python interpreter (with only the parts of stdlib that your code uses).

Start by evaluating PyOxidizer for opensafely-cli and determine the required platform-specific build outputs. Check how the current pip distribution handles Python and dependencies. Done means users can run binaries that include the selected Python version and dependencies without a system Python installation.