Don't automatically remove artifacts for pages jobs after pages:deploy has run

What does this MR do?

Prevents the pages:deploy pseudo-job from removing artifacts generated by the pages job immediately after running.

There's also a search-and-replace of Invaild -> Invalid in a separate commit.

Are there points in the code the reviewer needs to double check?

Why was this MR needed?

Automatic artifact removal following a pages deploy is extremely surprising, and undocumented. It also breaks CI pipelines when a later stage depends on the generated artifact.

It also makes it harder to divorce pages from a shared filesystem. This MR doesn't attempt to completely solve that problem - it just makes Pages artifacts be treated the same as any other artifact, so expiry will happen on normal timescales.

A future MR may want to pin the most recently-deployed artifact so that we can always rebuild the content of -pages-root from artifacts held by GitLab proper. We could even look to serving Pages sites directly from the artifacts via the API at some time in the future.

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Tests added for this feature/bug
• Review
  • Has been reviewed by Backend
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together
• Internationalization required/considered
• End-to-end tests pass (package-and-qa manual pipeline job)

What are the relevant issue numbers?

Closes #45481 (closed)