[Discussion] Seata and SkyWalking integration proposal

Hi Seata team,

I am glad to see the project has more contributors to join. As [Apache SkyWalking](https://github.com/apache/incubator-skywalking) creator, I am wondering, does Seata have interested to provides SkyWalking plugins, in order to observe how seata works with applications.

This is your architecture
Right now, SkyWalking could trace and provide metric for most RPC and DB accesses. Now if Seata could provide tracing based on SkyWalking agent plugin, which works between application and your TC, then user could see the status of seata, and have metrics(successful rate, latency, even topology) related to TC and whole distributed transaction.

I don't know whether this idea makes sense to seata team, since we already work with Dubbo and SOFA team tightly, I hope we could integrate on this point too.

If you have more ideas to discuss, and what we should do, we could discuss here.

Start by reading the discussion and the linked SkyWalking integration context, including the architecture image and the stated tracing and metrics goals. Clarify the proposed plugin scope and acceptance criteria with the Seata team; done would be an agreed integration plan or implementation path for observing Seata transactions and TC metrics.

Written by the indexing model from the issue text.