Merge remote-tracking branch 'upstream/v1.2.x' into upmerge_v12x

BUILD

cmake/msvc_static_runtime.cmake

grpc.gemspec

src/python/grpcio/grpc/_server.py

src/ruby/end2end/channel_closing_driver.rb

src/ruby/end2end/channel_state_driver.rb

src/ruby/end2end/end2end_common.rb

src/ruby/end2end/killed_client_thread_client.rb

src/ruby/end2end/killed_client_thread_driver.rb

src/ruby/end2end/sig_handling_driver.rb

src/ruby/end2end/sig_int_during_channel_watch_driver.rb

src/ruby/ext/grpc/rb_call.c

templates/grpc.gemspec.template

tools/run_tests/helper_scripts/pre_build_csharp.bat

tools/run_tests/helper_scripts/run_ruby_end2end_tests.sh