[Instrumentation.Http] Support for enrich and filter delegates for http client metric

[aunikitin]

Hello, I'd like to have an opportunity to enrich metrics with custom logic (for example uri templates of requested paths). Also I add opportunity to filter some requests because of TODO in MeterProviderBuilderExtensions
I tried to use existing HttpClientInstrumentationOptions but firstly, they have too mutch for metrics and secondly, because in the HttpHandlerMetricsDiagnosticListener we are not allowed to take tags from activity (because of uncontrolled source of filling), that's why delegates in settings don't fit .
Also I wrote some tests and did small refactoring in them (move trace tests in one file; split configuration tests from common, because they don't need running HttpListener).
If my changes are admissible, I will add description to CHANGELOG.md.

Probably it resolves issue

Changes

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For significant contributions please make sure you have completed the following items:

• Appropriate CHANGELOG.md updated for non-trivial changes
• Design discussion issue #
• Changes in public API reviewed