As opposed to a flat directory, we now have the following structure:

- security
  -context
  - credentials
    - composite
    - fake
    - google_default
    - iam
    - jwt
    - oauth2
    - plugin
    - ssl
  - transport
  - util

We have not refactored the test code yet but this PR is already large
enough...

C# finishing serverside request stream should not be required to dispose.

Add C# wrapping tests and fix some issues with the API.

Cleanup tools/jenkins directory

Allow directly specifiying connection path

Made Node tests support multiple versions and set the Node default version to 4 everywhere possible

Ruby docker files and config

Properly using our build.yaml source of truth to generate our list of public APIs.

Explicitly cast constant value to gpr_atm

Node tools: use the right extension for running protoc on Windows

C# cleanup client-side call RECV_STATUS_ON_CLIENT internals

Stress test fixes

Always build the grpc library when building the ruby extension.

Add C# stress client to the test framework

Disable fail fast for qps driver

Create Python stress test

Fix bug where max_frame_size was ignored