Remove `run_codegen.py` from python example.

Since we no longer reference `run_codegen.py` in the Quick Start for
Python, remove it from the repository to avoid confusion.

Remove hardcoding of clients/server names in run_sweep_performance.sh

Switch C# benchmarks to use CoreCLR

Add Shim for wakeup_fds with no pipe or 

gRPCLB and RR race fixes

Create filter for pull request tests on Jenkins

This also fixed a potential bug whereby callbacks wouldn't be called if
the pick happened immediately during the flushing of pending picks.

Fix clang-format problem from #8234.

Renamed LB-related metadata keys

Wrote C++ unimplemented_method interop test

Add calls' polling entities to the pollset_set of client_channel

update go in linux perf worker init script

Fix InteropTests.m bug

Allow pointer channel args python

Bug Fix in CSharp Interop Client

Add comment to NewInstance override in the generated code

More flexible test naming in XML reports