[WIP] Fix tornado server (request) duration metric calculation

[devmonkey22]

Description

Fix the tornado instrumenter to track a request's elapsed time in an async-safe way so concurrent requests calculate their own elapsed time for the HTTP_SERVER_DURATION metric properly.

Fixes #3486

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

I just used the existing automated tests to ensure no regressions occurred. I can explore further if we want to try to add concurrent request testing.

Does This PR Require a Core Repo Change?

• Yes. - Link to PR:
• No.

Checklist:

See contributing.md for styleguide, changelog guidelines, and more.

• Followed the style guidelines of this project
• Changelogs have been updated
• Unit tests have been added
• Documentation has been updated

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: devmonkey22 / name: Mike D (047bf3d)

[devmonkey22]

Question for review - with this change, do we think it needs a specific test, where we start 2 concurrent requests, staggered, then measure expected duration similar to opentelemetry-instrumentation-asgi test_asgi_middleware?