.arcconfig

hgcli: add stub PyOxidizer project

Using commit c772a1379c3026314eda1c8ea244b86c0658951d of
PyOxidizer, I ran `pyoxidizer init-rust-project hgcli` to
create a stub Rust project. The only modifications I made from
what that command produced are:

* Update location of pyembed crate to PyOxidizer's Git repository.
* Removed some trailing whitespace from pyoxidizer.bzl
* Added auto-generated Cargo.lock file

Subsequent commits will modify the stub project to Mercurial's
needs.

Differential Revision: https://phab.mercurial-scm.org/D8350

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