feat: add rest(HTTP) call trace propagation convenience method

[ShyunnY]

I looked through the source code and found that go-zero implements the propagation of calls between gRPCs through metadata.

• But the Rest HTTP call propagation seems to be lacking. I think that in some cases, we may use HTTP to call some third-party services or other internal services.

• At this time, we also need to propagate context in order to ensure the integrity of the trace.

• of course, we can complete the trace context building step at the logic layer, but I think this is not suitable. In the logic layer, you should not write too much code outside of the logic.

So I have a good suggestion. I hope to provide the encapsulation code of HTTP propagation in the trace package, which can make it easier to assemble the context of the propagation trace. I've written a PR code, but I'm not sure if go-zero needs this feature. Therefore raise this issue

[kevwan]

Would you please submit a PR? And we can have a discussion on this.

[github-actions[bot]]

This issue is stale because it has been open for 30 days with no activity.