Reposition files to optionalize client_config system

BUILD

Makefile

binding.gyp

build.yaml

config.m4

gRPC.podspec

grpc.gemspec

package.json

package.xml

src/core/ext/client_config/README.md

src/core/ext/client_config/channel_connectivity.c

src/core/ext/client_config/client_channel.c

src/core/ext/client_config/client_channel.h

src/core/ext/client_config/client_config.c

src/core/ext/client_config/client_config.h

src/core/ext/client_config/connector.c

src/core/ext/client_config/connector.h

src/core/ext/client_config/default_initial_connect_string.c

src/core/ext/client_config/initial_connect_string.c

src/core/ext/client_config/initial_connect_string.h