Support for `uv` within `python-bootstrap` subsystem

[zach-overflow]

Is your feature request related to a problem? Please describe.
It would be ideal if the python-bootstrap subsystem could rely on uv-installed Python interpreters, with a simple"<UV>" directive, similar to how the subsystem currently supports pyenv-installed interpreters via "<PYENV>".

This would also help to keep the number of tools required for a CI pants build step, particularly in projects which already rely on uv for package management.

If there already is support for this, then I think this feature request could become a documentation request.

Describe the solution you'd like
One-liner subsystem support for bootstrapping with uv-installed Python interpreters, ideally with the following simple syntax:

[python-bootstrap]
search_path = ["<UV>"]

Describe alternatives you've considered
There's maybe some alternative for hardcoding the uv-install path, but this request is specifically to enable support that is as simple as the "<PYENV>" directive, so I don't think there's a comparable alternative at the moment.

Additional context

• I saw this past issue, but my understanding is the current implementation is quite different from when that issue was created.