Calculate RPC deadline right before call creation

Working towards enabling a minimal stack

Refactor python code generator to support other serializers

Most core end2end tests are written around a single RPC with an explicit
deadline. Currently, this deadline is calculated before bringing up the
test fixture, and thus time spent bringing up the test fixture is taken
from the time allotted to the RPC.

This change moves the calculation of these deadlines immediately before
call creation. Additionally, the functions that calculate these
deadlines have been renamed from 'xx_seconds_time()' to
'xx_seconds_from_now()' for clarity.

Convert stream ops to a control + payload structure

Fix arena_test on 32-bit platforms (includes Windows)

Track milliseconds since process start in timer heap

Add option to limit # of messages per stream in QPS tests

Update readme.md

Remove complete_fetch and use complete_fetch_locked

Include new namespaces in the generated docs as well

Add 1MB ping pong scenarios

use markdown links style

Don't assert over invalid channel args

Split performance profile job in two

Fix duplicated NULL pointer check