Cherry-pick: Allow specifying a maximum run time to run_tests

Revert "Merge branch 'master' into v1.3.x"

This reverts commit 79759fea, reversing
changes made to dc36f4df.

Fixes for test stability (especially microbenchmarks)

Threaded port_server

Slow down timers for ubsan builds

Added unit testing support.

disable mongoose on v1.3.x

Add lock to shutdown_fd() callback in udp_server.c

Hybrid CQ support

Avoid duplication in Bazel rules by using grpc_cc_libraries rule-creator

Fix semantics of LB policy selection.

Fix HTTP proxy tests

Demote handshake logging msg to DEBUG

Track calls to gpr_now()

C++ compatibility fix for tmpfile_posix.c

C++ compatibility fix for stack_lockfree.c

- heap allocate the pollset shutdown closure (this may be called asynchronously)
- ensure a poller remains until all endpoints are closed