Merge pull request #12101 from grpc/revert-11977-tsi_grpc

BUILD

CMakeLists.txt

Makefile

binding.gyp

build.yaml

config.m4

config.w32

gRPC-Core.podspec

grpc.gemspec

package.xml

src/core/tsi/fake_transport_security.c

src/core/tsi/transport_security.c

src/core/tsi/transport_security.h

src/core/tsi/transport_security_adapter.c

src/core/tsi/transport_security_grpc.c

src/core/tsi/transport_security_grpc.h

src/core/tsi/transport_security_interface.h

src/python/grpcio/grpc_core_dependencies.py

tools/doxygen/Doxyfile.core.internal

tools/run_tests/generated/sources_and_headers.json