Log Message:
grpc: updated to 1.26.0

Release v1.26.0
This release contains refinements, improvements, and bug fixes, with highlights \ 
listed below.

Core
Fix compression filter crash on empty payload.
Ensure awake pollset_work threads exist on Windows.
Disable client_idle_filter.
Remove gpr_get/set_allocation_functions.
Security audit response.

C++
Automatically disable testing frameworks if gRPC_BUILD_TESTS=OFF.
Do not build channelz when gRPC_USE_PROTO_LITE.
Add options for all codegen plugins.
gRPC-C++ podspec follows gRPC versioning.
Issue 19208: Fix pollset_set_del_fd to cleanup all fd references.
De-duplicate .proto file processing.
cmake: Add VERSION and SOVERSION properties to libraries.

Python
Release Python3.8 wheels for Windows.
Release Python3.8 wheel on macOS.
Fix issue with exception being out of scope in Python 3.
[AIO] Implement the shutdown process for AIO server and completion queue.
Attempt to drop support for Python 3.4.
AIO Unified call interface.
Make sure Core aware of gevent Cython objects.
[bazel] Add an ability to call an optional custom plugin for py_proto_library \ 
and py_grpc_library.