No git clone for rspec:coverage job

From Draft to Ready

• !126851 (merged) is merged
• !127090 (merged) is merged
• !114109 (merged) is merged

Context

Related to #416630 (closed). Iteration 2 of #416630 (comment 1474093453).

What does this MR do and why?

We leverage the newly introduced .fast-no-clone-job job to avoid a git clone for the rspec:coverage job.

Instead, we download the necessary files from the GitLab API.

We also download local gems (see why in this comment).

Results

• Comparing the rspec:coverage job of this MR to another rspec:coverage job from outside this MR, we save 22 seconds .
  • 26 seconds for git clone versus 1 second.
  • 3 seconds added for downloading files from the API.
• Successful rspec:coverage job when ran against all specs: https://gitlab.com/gitlab-org/gitlab/-/jobs/4798732715
  • No git clone
  • Download the necessary files
  • Download the local gems (see why in this comment)

Next steps

See iteration 3 and 4 of #416630 (comment 1474093453).

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.