Reuse gRPC channels

[JoshYuJump]

Creating a channel can be expensive, so it’s better to reuse it for performance benefits.

We need a gRPC client factory offers a centralized way to configure channels. It automatically reuses underlying channels.

[JoshYuJump]

Closed as

Underlying our Python wrapper, the Channel object uses C-Core's Channel which will reuse existing connections. E.g. if you create 100 channel object to the same destination with same options, there will be only 1 outstanding TCP connection.
ref: grpc/grpc#20985 (comment)