refactor(uv step): check self update result if self-update feat is available

[SteveLauC]

What does this PR do

For the uv step, if the self-update feature is available, we should do the update and check its result.

cc @lucaspar

Standards checklist

• The PR title is descriptive
• I have read CONTRIBUTING.md
• Optional: I have tested the code myself
• If this PR introduces new user-facing messages they are translated

For new steps

• Optional: Topgrade skips this step where needed
• Optional: The --dry-run option works with this step
• Optional: The --yes option works with this step if it is supported by
  the underlying command

If you developed a feature or a bug fix for someone else and you do not have the
means to test it, please tag this person here.

[SteveLauC]

Thanks for reviewing!