[FEATURE] add gRPC service support

[kemingy]

Requirements:

• rust part doesn't parse the content, will pass all the bytes to python workers
• user can define their own protobuf file to serialize or de-serialize the data

[decadance-dance]

+1

[fighterhit]

+1. gRPC should be supported, after all, it is a widely popular method with higher performance than http1.x.

[kemingy]

+1. gRPC should be supported, after all, it is a widely popular method with higher performance than http1.x.

@fighterhit We already support HTTP/2 in #568, the performance won't be an issue.

[fighterhit]

+1. gRPC should be supported, after all, it is a widely popular method with higher performance than http1.x.

@fighterhit We already support HTTP/2 in #568, the performance won't be an issue.

Thanks @kemingy , but will it lack some GRPC features? https://grpc.io/docs/guides/

[kemingy]

Thanks @kemingy , but will it lack some GRPC features? https://grpc.io/docs/guides/

Which gRPC features do you want?