Enable cloud_to_prod_auth interop tests on Jenkins.

Bring Cython tests back online.

Enable timeout on sleeping server interop test

PHP: fix empty_stream interop test

Fix npm install failing to download Node headers in run_tests.py

Set current worker for longer

Metadata atomic magic

Added grpc_alarm (renamed previous one to grpc_timer)

Add Python support to run_interop_tests.py

Allow extra docker args to be passed to build_interop_image.sh

Bring Node coverage up to 95%

Fix call data init in census grpc filter.

Adds coverage reports for C and C++.

Add run_interop.sh jenkins script

Improving the C# auth API

Latency profiling support

C++ code generator plugin: eliminate use of nullptr