Moved protos out of core_codegen interface

BUILD

Makefile

build.yaml

gRPC.podspec

grpc.gemspec

include/grpc++/impl/codegen/core_codegen_interface.h

include/grpc++/impl/codegen/proto_utils.h

include/grpc/byte_buffer_reader.h

include/grpc/impl/codegen/byte_buffer_reader.h

package.xml

src/compiler/csharp_generator.cc

src/core/lib/transport/metadata.c

src/cpp/common/core_codegen.cc

src/cpp/common/core_codegen.h

src/csharp/Grpc.Examples/MathGrpc.cs

src/csharp/Grpc.HealthCheck/HealthGrpc.cs

src/csharp/Grpc.IntegrationTesting/MetricsGrpc.cs

src/csharp/Grpc.IntegrationTesting/ServicesGrpc.cs

src/csharp/Grpc.IntegrationTesting/TestGrpc.cs

test/core/surface/public_headers_must_be_c89.c