Revert "Renamed google_benchmark submodule to benchmark"

.gitmodules

Makefile

build.yaml

src/google_benchmark/gen_build_yaml.py

test/cpp/microbenchmarks/bm_fullstack.cc

test/cpp/microbenchmarks/noop-benchmark.cc

third_party/google_benchmark

tools/run_tests/sanity/check_submodules.sh

tools/run_tests/sources_and_headers.json

vsprojects/vcxproj/google_benchmark/google_benchmark.vcxproj

...vcxproj/google_benchmark/google_benchmark.vcxproj.filters