Clean up grpc++_unsecure so that it doesn't require secure content anymore

BUILD

CMakeLists.txt

Makefile

bazel/grpc_build_system.bzl

build.yaml

gRPC-Core.podspec

grpc.gemspec

package.xml

test/cpp/util/BUILD

tools/doxygen/Doxyfile.c++

tools/doxygen/Doxyfile.c++.internal

tools/doxygen/Doxyfile.core.internal

tools/run_tests/generated/sources_and_headers.json

vsprojects/grpc.sln

vsprojects/vcxproj/grpc++/grpc++.vcxproj

vsprojects/vcxproj/grpc++/grpc++.vcxproj.filters

vsprojects/vcxproj/grpc++_unsecure/grpc++_unsecure.vcxproj

...s/vcxproj/grpc++_unsecure/grpc++_unsecure.vcxproj.filters

vsprojects/vcxproj/grpc/grpc.vcxproj

vsprojects/vcxproj/grpc/grpc.vcxproj.filters