Rollup merge of #136911 - Kobzol:ci-helper-link, r=marcoieni

Add documentation URL to selected jobs

This PR adds the possibility to attach URLs to selected CI jobs, which are then printed at the end of the CI log when a failure happens in that job. The motivation is to allow contributors to find how to fix the specific jobs more quickly.

This was proposed on [Zulip](https://rust-lang.zulipchat.com/#narrow/channel/242791-t-infra/topic/Automatic.20useful.20links.20when.20a.20particular.20CI.20job.20fails.3F).

An example output can be seen [here](https://github.com/rust-lang/rust/actions/runs/13836290091/job/38712112523?pr=136911).

r? `@ghost`

Author: jhpratt