Subscribe error handling (#2785)

* [fix] etcd config source prefix issue (#2389)

* http transport data race issue (#2436)

* [fix] #2431 http transport data race issue

* [feature] Ability to close connection while receiving.
Ability to send messages while receiving.
Icreased r channel limit to 100 to more fluently communication.
Do not dropp sent request if r channel is full.

* [feature] always subscribes to all topics and if there is an error in one of them, the unsuccessful topics will be subscribed to again

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Co-authored-by: Johnson C <[email protected]>

Latest changes

Moving towards built in plugins

Adds grpc client/server/transport plugins

Version without cmd/protoc-gen-micro

New syntactic sugar

Bad commit

Support handler in service interface

Strip unused packages

Move back cmd package to top level

Cleanup Go Micro back to its essence. Fix all the tests.