To support magical internal build processes, the pb2 files need to be
split into pure-proto and gRPC parts. This performs that split and
further fixes bad module names in the test harness that interfered with
the intended test implementation.
An unfortunate side effect, due to limitations of protoc and holdover
behavior we must support in major version 1.x, is that trash files are
generated in split generation. This shouldn't be a problem in normal
protoc plugin use.
(1) Move dependency on protobuf from grpcio to grpcio_test. While the
most-commonly-foreseen use case of grpcio makes use of protobuf,
technically protobuf is not strictly needed and there's no actual
in-code relationship between grpcio and protobuf.
(2) Loosen the dependency on protobuf from ==3.0.0a3 to >=3.0.0a3.
(3) Update all references to 0.10.0* to 0.11.0.
(4) Alphabetize the grpcio_test dependencies.
Adds the initial reference implementation for health-checking in gRPC
Python as a separate project (but within the same grpc package to keep
namespaces consistent). Only installs the package to test the
build-proto-modules custom command introduced in the health-checking
project.