Switch from pip -> uv

[akan72]

Summary

• Porting over pip commands to uv (github), a drop-in replacement package manager + dependency resolver in order to improve build performance
• Use of a virtualenv is typically required, but the --system Astral/uv team mentions in the docs that doing a system-level install is fine within a CI environment
• Increase # of threads used in the dbt compile step in CI from 4 -> 16

Test Plan

• Executed commands locally

• dbt is installed + commands work in the CI environment for this PR

[simon-weber-artemis]

do we still need this line?

[akan72]

I think you're right, we don't use pip-compile or pip-sync in this repo anyway so it should be fine to remove.

pip should already be installed in the GH actions worker's system. But even if it isn't, uv can install for us which is p cool