FR: Alert users of expensive optimization in `tt update`

[tingerrr]

Description

When running tt update on tests which may take a long time to optimize, the reporter should print a hint that the optimization may be much slower than tt run. It should perhaps also suggest using --no-optimize-refs in combination with third party hosting (like Git LFS, oxen, or whatever game studios may otherwise use for their version controlled assets).

Adding an alert to the docs may also be helpful.

Additional Context

See #219, the lack of a message means that users don't know the expensive optimization is taking place.