Is your feature request related to a problem? Please describe.
Currently, the obsreport for receivers only support number of events sent successfully/failed. One new observability our application is looking for is the raw bytes the receiver receives for the events.

This raw bytes should be however much the receiver receives over the network. e.g: compressed bytes sent over HTTP.

Describe the solution you'd like
Updating obsreport to include new fields to include bytes.

// move to a struct so it is easier to extend without breaking signature
type observabilityData struct {
   numReceived int
   err error
   // optional. if nil, do not emit
   byteCount *int64
}

EndTracesOp(receiverCtx context.Context, format string, data observabilityData)
EndLogsOp(receiverCtx context.Context, format string, data observabilityData)
EndMetricsOp(receiverCtx context.Context, format string, data observabilityData)

Describe alternatives you've considered

• Considered adding this in our processor to count the bytes for each log record. However, this doesn't reflect true bytes received.
• Another consideration is creating a new extension to provide this functionality. Each receiver can choose to include this extension. However, the extension would act just like obsreport.

Additional Context
receivers equivalent github issue: #7310