Fix oss-fuzz/961

Further reduce noise

add doc for perf qps tests with steps for running

add installation of scipy and numpy in linux perf worker init

Max age for server channels

Fix build on mac

Tighten constraints for bm_diff to trigger

Add selected fullstack benchmarks to pr suite

Fix bm_diff

This reverts commit 1463d0e7.

Loosen constraints for reporting

Add a preparatory LTO target

A better bm_diff

Add C++ large message performance tests to PRs and master

Removed wrong LR include from codegen

Display time between objc tests

Do not call grpc_init() for per-call-completion-queues created by a C++ sync server

Add instructions to install libgflags-dev, libgtest-dev, clang and libc++-dev