This change modifies the BUILD rule dependencies used for nanopb,
switching them from third_party to //external -- the former uses
submodules, which don't work well with Bazel (since Bazel removes
submodules from repositories as it fetches them, preferring instead to
unify submodule versions across the workspace via the top-level
WORKSPACE configuration).

Objective C: kSCNetworkReachabilityFlagsIsWWAN is only available on iOS

Stress test flexible config

C# performance worker improvements

Follow Node's callback-last convention for client calls

Make IP_PKTINFO optional.

Optionalize chttp2

Fix some status codes to match spec

(opt-tsan-asan.json) and short term test runs (opt.json)

Begin core componentization

different projects with the same configuration

Moving grpc_pick_unused_port_of_die before creating a deadline.