Opentelemetry integration: Support for http exporter

Currently you can only export as grpc.
It would be really nice to export as http also.

Hello, @hans and welcome to the Buildkite Community!
Thank you for your feedback! As far as I know, we have no immediate plans of implementing support for HTTP exporter. However, you can open an issue regarding your request on the Buildkite agent repository to bring it to the attention of our Developer team.