OpenTelemetry support in worker

[andystaples]

Initial commit of changes needed to support OpenTelemetry in the worker

• Includes the ability to check for the presence of the AzureFunctions.PowerShell.OpenTelemetry.SDK module and run commands from that module
  • Initializes an internal activity before each function invocation to link worker traces to host
  • Takes a reference to a method from the module and forwards all logs back through this method to be passed on to the OTel endpoint
• Report the relevant OTel worker capabilities at init based on the presence of a newly specified environment variable
• Update protobuf spec to latest in order to
  • Support updating worker capabilities at EnvironmentReloadRequest
  • Provide this capability for apps which were started in placeholder mode

resolves #1048

Pull request checklist

• [ ] My changes do not require documentation changes
  • [ ] Otherwise: Documentation issue linked to PR
• [ ] My changes should not be added to the release notes for the next release
  • [ ] Otherwise: I've added my notes to release_notes.md
• [ ] My changes do not need to be backported to a previous version
  • [ ] Otherwise: Backport tracked by issue/PR #issue_or_pr
• [ ] I have added all required tests (Unit tests, E2E tests)

Additional information

Additional PR information

[andystaples]

This is a draft PR for a number of reasons. We need to discuss:

• Any concerns with the additional checks for the presence of the OTel module
• Cold start impact
• Additional testing that may be required (?)

Also, there is a comment in there (RequestProcessor#400) that suggests some uncertainty about whether all worker capabilities need to be reported in EnvironmentReloadRequest. Reading through the protobuf spec, the host defaults to "merge" mode where new capabilities are added but old ones are retained, so that is no longer a concern. I'll pull that comment out with the next commit to this branch