test-util: allow filtering metrics by scope

[anuraaga]

Description

Adds a parameter to get_sorted_metrics to filter by scope name to allow the SDK to generate its own metrics and not affect instrumentation. By default, the SDK metrics are filtered out, while instrumentation can instead provide their own scope name to fetch metrics by scope, which can be used like in ASGI to reduce heavy for looping to assert scopes

As it's test-util only I figure it can be skip-changelog

This has been extracted from #4880

@xrmx to help review

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?

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

• Unit tests

Does This PR Require a Contrib Repo Change?

• Yes. - Link to PR:
• No.

Checklist:

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