fix: use existing ui instead of constructing a new one (#5886)
### Description
In `run` and `prune` we were using a `UI` that always disabled colors
and ignored any user flags or env vars. This PR switches us to use the
`UI` struct that was passed in.
### Testing Instructions
👁️
Closes TURBO-1302
Co-authored-by: Chris Olszewski <Chris Olszewski>
