[Exporter.OpenTelemetryProtocol] Support for Compression

[Kielek]

Feature Request

Supoort for the compresion env. vars in the OTLP exporter.
Specfication: https://github.com/open-telemetry/opentelemetry-specification/blob/0a4c6656d1ac1261cfe426b964fd63b1c302877d/specification/protocol/exporter.md?plain=1#L39-L41

Describe the solution you'd like:

Possibility to configure compression based on appropriate class properties and env. varriables - like in specification.

Describe alternatives you've considered.

N/A

Additional Context

Request from @otel0dotnet-atuo-instr slack channel https://cloud-native.slack.com/archives/C01NR1YLSE7/p1669828204249379

[anchlovi]

+1 - request size grows quickly in high throughput environments

[djluck]

As a workaround, you can enable compression for the GRPC-based client by adding grpc-internal-encoding-request to OtlpExporterOptions.Header:

AddOtlpExporter(x =>
{
    x.Endpoint = new Uri("http://localhost:4317");
    x.Headers = "grpc-internal-encoding-request=gzip";
}

This works as the Header collection is propagated to the GRPC Metadata collection. Metadata is used by the GrpcNetClient to set the compression algorithm: https://github.com/grpc/grpc-dotnet/blob/master/examples/Compressor/Client/Program.cs#L38