Byte rate metrics

### 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.

I would be interested to know how many bytes are read/written from/to the ASP.NET Core sockets to understand more how much data is my server processing. That could for example explain why the load on my server is increasing even though the number of requests did not change.

### Describe the solution you'd like

Two new metrics for ASP.NET Core:
- `aspnetcore.request.bytes_read`: number of bytes read from the sockets
- `aspnetcore.response.bytes_written`: number of bytes written to the sockets

OTEL doesn't seem to define a convention for byte rates: https://opentelemetry.io/docs/specs/semconv/http/http-metrics.

### Additional context

_No response_