C# add microbenchmarks project

Remove uneeded ref/unref

Fix sanity

clang-format and include guard fix

Improve contributing guidelines

Fix Python reflection arguments

Fixes #9542

Remove the section for b64 encoded trailers.

Remove the section for b64 encoded trailers. As gRPC-Web uses CRLF to separate the trailers in the trailers frame, a binary trailer need to reserve in a base64 encoded format for their values. This cannot be skipped even base64 is applied on the whole trailers frame per client's request via content-type: application/grpc-web-text.

Intrusive hash map

Refcounting fix

 Update security_handshaker to use new TSI

Refactor some code and document most of the API

Add api to server builder plugin to modify the builder

Fix sanity

Export function gpr_log_severity_string for grpc_csharp_ext

PHP: Fixed bug in protoc plugin escaping comments

More Doxygen comment improvements.