constant state watch without timeouts

src/ruby/end2end/channel_closing_driver.rb

src/ruby/end2end/channel_state_driver.rb

src/ruby/end2end/grpc_class_init_client.rb

src/ruby/end2end/grpc_class_init_driver.rb

src/ruby/end2end/sig_int_during_channel_watch_client.rb

src/ruby/end2end/sig_int_during_channel_watch_driver.rb

src/ruby/ext/grpc/rb_call.c

src/ruby/ext/grpc/rb_channel.c

src/ruby/ext/grpc/rb_completion_queue.c

src/ruby/ext/grpc/rb_completion_queue.h

src/ruby/ext/grpc/rb_event_thread.c

src/ruby/ext/grpc/rb_server.c

src/ruby/spec/channel_connection_spec.rb