fix(instrumentation-http) Added ATTR_HTTP_ROUTE to the new metric attributes

[lionskape]

Which problem is this PR solving?

There is no way to create http.route attribute for server metric in "stable-only mode" for http metrics.

Fixes # (issue)

Short description of the changes

Added ATTR_HTTP_ROUTE setup in "stable-only mode" for METRIC_HTTP_SERVER_REQUEST_DURATION in @opentemetry/instrumentation-http

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)

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration

• switch to stable-only mode in @opentemetry/instrumentation-http
• add rpc metadata http route, check that metric attribute exists
• remove rpc metadata http route, check that metric attribute does not exists
• switch to dup mode in @opentemetry/instrumentation-http
• add rpc metadata http route, check that metric attribute exists in both stable and old metrics
• remove rpc metadata http route, check that metric attribute does not exists in both stable and old metrics

Checklist:

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

[linux-foundation-easycla]

• ❌ - login: @lionskape / name: Vladimir Ulyanov . The commit (ec3aaed, 7fcbd4e) is not authorized under a signed CLA. Please click here to be authorized. For further assistance with EasyCLA, please submit a support request ticket.

[pichlermarc]

Hi @lionskape - thanks for reaching out. I looked into it and this is indeed a bug in this unreleased feature that has a few more layers to this bug that also involve span attributes and other metric attributes, so the fix is not as simple as it is proposed here.

I opened #5081 to take care of this.

[lionskape]

@pichlermarc hello. Thank you for your attention. I will discard my PR in favor of your chagnes.