PHP: update README and apache/nginx examples

Port #9505: Fixes for gRPC ObjC v1.1.0 release

Add a test verifying number of writes per RPC is reasonable

shorten qps worker timeouts and run remote workers under timeout

Add some debug utilities

Test CMake build on Linux and Windows continously

add missing return in scenario config

always render junit xml report after perf tests

Add an on_write callback to the UDP server.

This PR adds a set of debug helpers that are intended for calling only from gdb. They cross abstraction boundaries and allow quickly accessing one thing from another thing.
I expect to grow this library significantly over time to aid debugging tricky problems.

cmake buildfile improvements

Fixed invalid handling of slice data in interop_server

One-way streaming microbenchmarks