feat: add enum support to instrumentation base

[robertlaurin]

[plantfansam]

Hello, and thank you for your contribution!

We recently split Ruby instrumentation out into the opentelemetry-ruby-contrib repo.

This PR is related to instrumentation, so we'll need you to re-open it against opentelemetry-ruby-contrib. Sorry for the inconvenience!

To do that, you can:

1. Create a fork of opentelemetry-ruby-contrib and copy the git url
2. In your opentelemetry-ruby repo, run git remote add tmp-contrib <your-fork-git-url>
3. git push tmp-contrib your-branch-name
4. Open a new PR in contrib (feel free to just copy/paste your original PR description there)
5. Close your open PR in this repo with a comment that links to your new PR in contrib
6. Delete your tmp-contrib remote from opentelemetry-ruby (git remote rm tmp-contrib)
7. git clone your opentelemetry-ruby-contrib fork, check out your branch, and make all changes in that repo from now on!

Sorry again for the inconvenience, and thank you for contributing!

[github-actions[bot]]

👋 This pull request has been marked as stale because it has been open with no activity. You can: comment on the issue or remove the stale label to hold stale off for a while, add the keep label to hold stale off permanently, or do nothing. If you do nothing this pull request will be closed eventually by the stale bot

[kaylareopelle]

Hi, @robertlaurin! Based on a recent SIG conversation, I'm closing PRs related to instrumentation in this repo. If you think this would still be helpful, please reopen in the opentelemetry-ruby-contrib repo. Thank you!