Support environment lacks pip

[T-256]

I use Rye as python project manager, One if its features is:

• No Default Dependencies: the virtualenvs when they come up are completely void of dependencies. Not even pip or setuptools are installed into it. Rye manages the virtualenv from outside the virtualenv.

Which then vscode-python-manager extension unable to manage packages in venvs created by Rye.

[T-256]

I think the solution would be instead of relying on environment's specific pip/pkg-manager, use unified external pkg-manager. I'd recommend that this extension have bundled UV tool inside itself for this purpose.