Backport of grpc#26220 to v1.38.x. This is the only backport, since the EventEngine code was introduced after v1.37 was cut.

This file is needed for the Objective-C cocoapod build.

…c#26282) (grpc#26288)

Co-authored-by: Mark D. Roth <roth@google.com>

* Enable Traffic Director time tracer (grpc#26111)

* Just update the timeout (grpc#26223)

* Increase xds job timeouts (grpc#26187)

* Revert grpc_xds_k8s job timeouts back to 120 mins (grpc#26219)

* Revert grpc_xds_k8s_python timeout to 120mins (grpc#26221)

Seems to have been inadvertently increased in grpc#26187

Co-authored-by: Eric Gribkoff <ericgribkoff@google.com>
Co-authored-by: Yash Tibrewal <yashkt@google.com>

* Bump version to v1.38.0

* Regenerate projects

…rpc#26283) (grpc#26313)

* Provide custom sponge configs

* Correct the script

* Allow test scripts to produce artifacts through Docker

* Overcome the direcotry clone in our docker script

* Expose TESTGRID_EXCLUDE and GIT_ORIGIN_URL through docker run

* Make sanity tests happy

…tgrid (grpc#26283) (grpc#26313)" (grpc#26324)

This reverts commit 54dc182.

* workaround grpc#26279 at the expense of binary compatibility

* correctly tag aarch64 wheels as manylinux_2_24

* remove unnecessary comments left by grpc#26430

* upgrade dotnet SDK 3 for C# build

* add C# global.json

* install dotnet SDK 3 on macos

* upgrade C# docker images to debian buster

* regenerate dockerfiles

* switch remaining tests to C# buster image

* remove C#'s global.json (which requires dotnet SDK 3+)

* dotnet SDK3 currently breaks C# package build

* regenerate dockerfiles