Trim down metrics cardinality

[nikola-jokic]

Runner ID increases metrics cardinality, since all runners are ephemeral.

To address this problem:

• Exclude runner_id and runner_name from all metrics labels
• Exclude job_workflow_ref and the job_name from the histogram

In the future releases, it should be considered adding configurable labels. However, removing the labels mentioned above makes sense since they increase cardinality substantially. If there is a need to return them back, we can do it in the same time when configurable metrics are introduced.

Fixes #2873

[MPV]

Did this PR remove these labels from both:

• gha_job_execution_duration_seconds
• gha_job_startup_duration_seconds

We are seeing lowered cardinality on: 🙏🏻

• gha_job_startup_duration_seconds

But still high cardinality on: 😅

• gha_job_execution_duration_seconds (especially the _bucket)