Make UV_PYTHON_INSTALL_MIRROR configurable in uv.toml

[Vynce]

Please consider making UV_PYTHON_INSTALL_MIRROR and UV_PYPY_INSTALL_MIRROR configurable in the user-scoped uv.toml config file. I think this is a separate use case from the similar pyproject.toml request in #8166.

Related:
#8015
#8068

[zanieb]

I have no problem with supporting this!

[paveldikov]

I mentioned this somewhere else, but this would be a good one for enterprises who may want to adopt uv python install (and derivative functionality that may happen in future e.g. #6970) in a way that complies with internal security policy/tooling.

[benjs]

With my issue #8166 I did not mean to specify it in exactly pyproject.toml, I am also fine if it can be specified somewhere else with the code :)
So I also would support this !