python: consider making PET default interpreter locator

[isabelizimm]

With the speed enhancements, we will want to eventually make the PET (Python Environment Tools) the default locator for Python environments.

[austin3dickey]

We probably want to polish interpreter names before turning this on by default:

• Polish naming of python interpreters in dropdowns #6705

[isabelizimm]

We may want to follow whenever upstream changes its default microsoft/vscode-python#25258

other possible issues to investigate

• python: native locator doesn't find base uv pythons on Windows #8005
• https://github.com/posit-dev/positron-builds/issues/444