ci: add workflow to update otel dependencies

[pichlermarc]

Which problem is this PR solving?

We currently have to update @opentelemetry/* dependencies by manually opening a PR to do so (see #2535, for example). With the script that @trentm added (scripts/update-otel-deps.js) this process is almost fully automated already, and just has to be reviewed by a human.

This PR adds a workflow that makes @opentelemetrybot open the PR based on the changes made by the script, similar to how release PRs work in the core repo.

Ideally this workflow will help us spread the load of releasing even further by making it a bit simpler. Once merged and once we've tried running it - I'll update the core repo's releasing.md to include the instructions to run this workflow. We may even be able to have it run automatically when there's a new OTel JS core release. 🙂

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.75%. Comparing base (bc647fc) to head (c28cc7b).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2536      +/-   ##
==========================================
- Coverage   90.80%   90.75%   -0.05%     
==========================================
  Files         169      169              
  Lines        8018     8018              
  Branches     1632     1632              
==========================================
- Hits         7281     7277       -4     
- Misses        737      741       +4     

see 1 file with indirect coverage changes

[trentm]

• The first time this workflow fails I'll want to see the output with DEBUG=1 ... turned on. I guess we could run it locally to try to reproduce the failure. Eventually we may want a way to run the workflow with DEBUG=1.
• Currently update-otel-deps.js will console.warn(...) in some cases and carry on. Should we (I could) change the script (possibly optionally, or make it the default) to fail for those cases? One warning case is when the script notices that not all otel deps were updated (usually for some complex transitive dep issue).
• Would we notice if this update script failed? I don't regularly look at https://github.com/open-telemetry/opentelemetry-js-contrib/actions for failed workflow runs. Do you know if there an prior art in any OTel repos for notifications from GH Action workflows?