[feature request] Metrics OpenTelemetry

[wrwsc]

Component

OpenTelemetry.Instrumentation.Runtime

Is your feature request related to a problem?

Why do metrics (for example, Runtime) use UpDownCounter or Counter instead of Gauge, when Gauge is the right metric?

https://github.com/open-telemetry/opentelemetry-dotnet-contrib/blob/main/src/OpenTelemetry.Instrumentation.Runtime/RuntimeMetrics.cs

What is the expected behavior?

I would like to understand why the gauge does not change after taking a snapshot.

Which alternative solutions or features have you considered?

None

Additional context

None

[github-actions]

Tagging component owner(s).

@twenzel @xiang17