Minor cleanup on QPS tests

Avoid TSAN reported lock cycle

Support service configs in core.

Fix config-exclusion for secure variants of tests

Change channel tests to use public API

Update projects to XCode 8, and Swift sample to Swift 3

C++ Now Runs All Interop Tests

change from malloc to gpr_malloc

Wakeup fds on bad poll

Refactor C# NoSuchMethodCallHandler

Design docs

This allows for testing other implementations of grpc.Server.

All current interop tests are implemented for C++ client and server. Updated run_interop_tests.py so that C++ no longer skips any tests

Fix status_code_and_message interop test for C++ and PHP.  Change run_interop_tests.py to run this test for C++ and Go.

Server context test spouse

Move back to a mostly-single-threaded http2 transport

Fix php interop client for status_code_and_message test

Remove `run_codegen.py` from python example.

Since we no longer reference `run_codegen.py` in the Quick Start for
Python, remove it from the repository to avoid confusion.

Remove hardcoding of clients/server names in run_sweep_performance.sh

Switch C# benchmarks to use CoreCLR