trace: tag http.route on api-gateway spans

[Julio-Guerra]

What does this PR do?

Add the missing http.route span tag to api gateway spans.

Motivation

Support the APM's API Catalog which needs this span tag to list their entries in the API Catalog.

Testing Guidelines

TODO

Additional Notes

Types of Changes

• [ ] Bug fix
• [ ] New feature
• [ ] Breaking change
• [ ] Misc (docs, refactoring, dependency upgrade, etc.)

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• [ ] This PR's description is comprehensive
• [ ] This PR contains breaking changes that are documented in the description
• [ ] This PR introduces new APIs or parameters that are documented and unlikely to change in the foreseeable future
• [ ] This PR impacts documentation, and it has been updated (or a ticket has been logged)
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