Simplify client channel pipeline setup (#1064)
Simplify client channel pipeline setup (#1064)

Motivation:

The client pipeline setup got a little complicated as it involves
calling various configure function and then adding handlers to various
ohter points. As such we end up creating a bunch of unnecessary futures.

Modifications:

- Create an array of handlers we expect to add to the client pipeline

Result:

- Code is simpler and easier to understand where each handler fits in.
- I'd expect a small perf gain on connection setup but this wasn't measured.
grpc/grpc-swift,grpc/grpc-swift,grpc/grpc-swift,grpc/grpc-swift,grpc/grpc-swift