C++ Bazel files

Initial test/cpp/util/BUILD file.

PHP: add macro for arg info in extension

Restore the NextMessageSize for streamed calls

Use special errors where appropriate in call cancellation: avoids many allocations in a semi-common case

Export LICENSE.txt in //third_party/nanopb

Add random samping to run_tests.py

Convert client_channel.c to use a combiner lock

Connect to "localhost" from interop clients.

Remove network_status_tracker code

Use special errors where appropriate in call cancellation: avoids many allocations in a semi-common case

make grpc-encoding:identity implicit

Use call context to propagare LR costs

Better error reporting in run_tests.py

Fix escaping in index.html

Add benchmarks of closures, combiners, exec_ctx primitives