Move protos to opentelemetry-proto repo.

[bogdandrutu]

No description provided.

[kaushikchaubal]

Looks like changes for this was merged, right? Is it worth closing the issue?

[pavolloffay]

The protos have been copied but they are still here https://github.com/open-telemetry/opentelemetry-java/tree/master/sdk/src/main/proto. Maybe it would be better to consume them as a git submodule.

[kaushikchaubal]

Do you want me to create a git submodule for https://github.com/open-telemetry/opentelemetry-java/tree/master/sdk/src/main/proto then? If so, I can aim to create a PR for that.

[pavolloffay]

Let's see what others say, I think it's a good idea.

[songy23]

+1 to git submodule.