Use APL-2 compatible existing code

[nightlyone]

FYI @adamko147 Most of the needed transformations are already in https://github.com/open-telemetry/opentelemetry-collector-contrib/blob/a0394170a1952c181b6a2735a0e553c4d676be78/exporter/azuremonitorexporter/trace_to_envelope.go but sadly it is not exported.

The code is available under the same license as yours.

Maybe that helps you to make progress on that great project.