[CI] Adjust workflows so that they run on merge_group too

[chalin]

References:

• https://docs.github.com/en/repositories/configuring-branches-and-merges-in-your-repository/configuring-pull-request-merges/managing-a-merge-queue#triggering-merge-group-checks-with-github-actions

  

• https://cloud-native.slack.com/archives/C06EDFPQ5EH/p1722946306243659?thread_ts=1722946011.805849&cid=C06EDFPQ5EH

[chalin]

@open-telemetry/docs-maintainers - please comment here once you are able to confirm that the workflows indeed trigger on a merge-group event. I'll reopen this issue until we get that confirmation. Thanks.

[chalin]

Ah, I see that merge_group events are being processed. We can actually filter for this kind of event: https://github.com/open-telemetry/opentelemetry.io/actions/workflows/check-links.yml?query=event%3Amerge_group

For example, see https://github.com/open-telemetry/opentelemetry.io/actions/runs/10322514304:

The hash links to 1e4f5b2. So I assume that the commit hash was the result of a PR update applied to #5015 while it was in the merge queue.

So, it seems to be working as expected. I'm going to close this now. Feel free to reopen if there's something that I missed.