Wrap scheduler tasks in Open Telemetry spans

Hey, I just made a Pull Request!

This PR changes the scheduler so that tasks are wrapped in Open Telemetry spans.

Before this change, when trying to troubleshoot a scheduled task through an OTEL trace, spans would be incorrectly grouped. This lead to the scheduled task being split in many traces. By adding a span around the task itself, all the work a task does can now be grouped into that task in a single span.

:heavy_check_mark: Checklist

• [x] A changeset describing the change and affected packages. (more info)
• [ ] Added or updated documentation
• [ ] Tests for new functionality and regression tests for bug fixes
• [ ] Screenshots attached (for UI changes)
• [x] All your commits have a Signed-off-by line in the message. (more info)

Changed Packages

Package Name	Package Path	Changeset Bump	Current Version
@backstage/backend-defaults	packages/backend-defaults	patch	v0.5.0-next.0

👋 @Rugvip It's been a little while this PR hasn't seen updates. Can you take a look. I believe that I've addressed your comments.

This PR has been automatically marked as stale because it has not had recent activity from the author. It will be closed if no further activity occurs. If the PR was closed and you want it re-opened, let us know and we'll re-open the PR so that you can continue the contribution!

Thank you for contributing to Backstage! The changes in this pull request will be part of the 1.31.0 release, scheduled for Tue, 17 Sep 2024.