[CI] python CI should use an image that has a UV package vs downloading uv each build

[rysweet]

What happened?

the CI scripts download uv and this has proven occasionally brittle and is a potential attack vector. we should shift to using an image or package that includes it already.

What did you expect to happen?

need to have uv out of the box in ci

How can we reproduce it (as minimally and precisely as possible)?

run CI disconnected or look at prior failures in GH actions logs

AutoGen version

all

Which package was this bug in

Core

Model used

No response

Python version

3

Operating system

CI (linux)

Any additional info you think would be helpful for fixing this bug

No response