Improvements to the way we randomize test runs.

Removed grpc_byte_buffer_reader_{create,destroy}.

Enable service_account_creds test and compute_engine_creds for gRpc-java.

Bump C# package versions

Corrects the cancel_after_first_response test

Avoid polluting our compilation with previously installed grpc.

Fix version number of gRPC.podspec

Fix NSDictionary <-> metadata codec

Fixed memory leak in server_async

And solves a few linter issues that prevent it from being submitted to Cocoapods' repo.

As a no-op for the time being.

Swapping the library order so that anything that openssl requires is properly tagged afterward.

Label all iomgr objects

- stops attempting to verify by catching the CancelledError

- instead the test examines the operation state after cancellation,
  which is equally valid and more stable.

Also
- simplifies bidi on the server

Add a completion queue test

run_tests.py support for C# on windows

Introduced grpc_byte_buffer_init instead. It's now the user's responsibility to
manage memory.

Fix bug with finite runs per test

Conflicts:
	src/core/iomgr/fd_posix.h
	src/core/iomgr/iomgr.c

Various minor fixes

Fixing tools compilation.

- create completion queue
- call shutdown
- call next

Revamped iomgr's callback mechanism

Initial Census refactoring and context integration