SignalR .NET client telemetry

### Is there an existing issue for this?

- [X] I have searched the existing issues

### Is your feature request related to a problem? Please describe the problem.

The SignalR .NET client doesn't have telemetry. This is a gap compared to .NET clients for HTTP and RPC. `HttpClient` and `GrpcChannel` have metrics and activities for tracking usage.

### Describe the solution you'd like

SignalR .NET client should have metrics:

* Conenction-level metrics. This would be similar to the metrics offered on the server.
* Invocation-level metrics. e.g. current active invocations, invocation duration

And it should create an activity for invocations so they show up in tracing.

### Additional context

_No response_