Add support for `uv` managed interpreters

[zeevro]

uv is a great tool by astral-sh (makers of ruff) that can install and manage python interpreters. It would be nice if pet could find these interpreters.
(see: https://github.com/astral-sh/uv)

[T-256]

(doing that isn't even useful, as these installations are externally managed).

Use case of externally managed environments like uv's installed interpreters is to create new venvs by them. I think intent in here was also to not manage/modify those environments but instead using them to manage venvs.

[karthiknadig]

Supported via #263