Add support for an OpenTelemetry trace/span reporter

[pnerg]

Kamon needs to add support for exporting traces according to the OpenTelemetry Protocol (OTLP).

This ticket is added as a placeholder as I intend to donate my ongoing implementation kamon-otel-trace-exporter once I have it in decent shape.

[SimunKaracic]

We eagerly await your donation, feel free to open a WIP pull request or ask for help!

[pnerg]

@SimunKaracic just did an integration test with the exporter and the released w3c context propagation....resulted in #975 :)

Apart from that the code is in working condition. Will make a PR soonish, the only thing I'll leave out is support for TLS.
Think that can come in a later release. Guess there's very few apps actually using TLS for reporting trace data.