Support for uv

[t-kalinowski]

uv is a fast and efficient package management tool. We should consider adding support for it in reticulate.

One of its key advantages is that it allows for installing a specific Python version on demand in the same motion as setting up the virtual environment. This capability eliminates the need for users to first ensure a suitable Python venv starter is pre-installed (e.g., by running install_python()). It also avoids the need for reticulate to search for and locate suitable virtualenv_starter()s. This feature could streamline the user experience.

The ability to install a specific Python version on demand means that uv could serve as a drop-in replacement for many uses of conda. Importantly, it sidesteps the potential risk of binary incompatibilities that conda usage introduces.