Remove OtlpExporter resource modification code

[CodeBlanch]

We have some code in OtlpExporter which will add service name if it isn't found on the resource:

• opentelemetry-dotnet/src/OpenTelemetry.Exporter.OpenTelemetryProtocol/Implementation/ResourceExtensions.cs

  Lines 23 to 32 in 9f41ead

  	if (!processResource.Attributes.Any(kvp => kvp.Key == ResourceSemanticConventions.AttributeServiceName))
  	{
  	var serviceName = (string)ResourceBuilder.CreateDefault().Build().Attributes.FirstOrDefault(
  	kvp => kvp.Key == ResourceSemanticConventions.AttributeServiceName).Value;
  	processResource.Attributes.Add(new OtlpCommon.KeyValue
  	{
  	Key = ResourceSemanticConventions.AttributeServiceName,
  	Value = new OtlpCommon.AnyValue { StringValue = serviceName },
  	});
  	}

• opentelemetry-dotnet/src/OpenTelemetry.Exporter.OpenTelemetryProtocol/Implementation/Serializer/ProtobufOtlpResourceSerializer.cs

  Line 59 in 9f41ead

  otlpTagWriterState = ProcessResourceAttribute(ref otlpTagWriterState, new KeyValuePair<string, object>(ResourceSemanticConventions.AttributeServiceName, DefaultServiceName));

Discussed with @alanwest and neither of us feel this should be done. The OtlpExporter should just respect what the SDK resource has.

What needs to be done...

• Remove this logic
• Call it out as a breaking change on CHANGELOG

[rajkumar-rangaraj]

@CodeBlanch / @alanwest Could you please check if this logic also needs to be removed? There is similar code in the OTLP tag parser to populate peer.service. I don't see this as part of the semantic specification.

opentelemetry-dotnet/src/OpenTelemetry.Exporter.OpenTelemetryProtocol/Implementation/ActivityExtensions.cs

Line 338 in 9f41ead

private struct TagEnumerationState : PeerServiceResolver.IPeerServiceState

Test:

opentelemetry-dotnet/test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/OtlpTraceExporterTests.cs

Line 721 in 9f41ead

public void ToOtlpSpanPeerServiceTest()

[alanwest]

There is similar code in the OTLP tag parser to populate peer.service.

Agreed that this should also be removed.

In conversation with @rajkumar-rangaraj he also raised the point that these changes are breaking. My opinion is that while these changes are breaking, I'd really just consider them bugs. Bug fixes usually change behavior, so much of the time they're "breaking", but I'd just call them out as bug fixes and not a breaking change.