Zipkin exporter must support Zipkin v1 thrift format

[codeboten]

As per spec: https://github.com/open-telemetry/opentelemetry-specification/blob/master/specification/trace/sdk_exporters/zipkin.md#considerations-for-legacy-v1-format

[robwknox]

@codeboten i'll take this as well.

[robwknox]

Here is a Staged PR with completed code to give visibility while waiting on dependent PRs (#1318 and #1173) to be approved & merged.

[github-actions]

This issue was marked stale due to lack of activity. It will be closed in 30 days.

[codeboten]

@robwknox just wanted to check if you were interested in getting that PR opened, even if someone else has to take it over the finish line.