Support `pyoxidizer run --example <NAME>`

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Thanks for the awesome work you're doing here!

I'd like to have some integration type tests via running examples, typically done with `cargo run --example some-example`. My project is of the _Python-flavored_ Rust code variety.

Is this possible to do with PyOxidizer? I've naively tried with `pyoxidizer run --example` but of course that fails as there's no option for it. And I suppose the same applies for `cargo test`, I'm not sure how to run Rust tests which make use of the Python interpreter via PyOxidizer.

Is there an alternative, or perhaps I'm missing something obvious :question:

Start by tracing how the `pyoxidizer run` command handles arguments and compare it with the requested `cargo run --example ` workflow. Then investigate how `cargo test` could run Rust tests that use the Python interpreter; done means the supported example and test workflows are clearly defined and usable.

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