Log Message:
grpc: updated to 1.39.0

Release v1.39.0

This release contains refinements, improvements, and bug fixes, with highlights \ 
listed below.

Core

Initialize tcp_posix for CFStream when needed.
Update boringssl submodule.
Fix backup poller races.
I am back.
Use default port 443 in HTTP CONNECT request.

C++

New iomgr implementation backed by the EventEngine API.
async_unary_call: add a Destroy method, called by std::default_delete.
De-experimentalize C++ callback API.

C#

[C#] Add ChannelCredentials.SecureSsl property for better codecompletion with \ 
ChannelCredentials.
Better way of building protoc aarch64 artifacts.
Add C# plugin "file_suffix" option defaulting to "Grpc.cs".
Add "GeneratedCode" attribute to generated service stubs.

PHP

PHP: stop reading composer.json file just to read the version string.

Python

Python AIO: Match continuation typing on Interceptors.
Workaround 26279 by publishing manylinux_2_24 wheels instead of manylinux2014 on \ 
aarch64.
Fix zlib unistd.h import problem.
Handle gevent exception in gevent poller.

Ruby

Set XDS user agent in ruby via macros.