Revert "[benchmarks] Move libcxx's fork of google/benchmark and llvm/utils'"

This reverts commit c6f7b720ecfa6db40c648eb05e319f8a817110e9.

Some buildbots are failing, will investigate and reland.
Example:
  https://lab.llvm.org/buildbot#builders/138/builds/14067
  https://lab.llvm.org/buildbot#builders/73/builds/20159
GitOrigin-RevId: e7568b68da8a216dc22cdc1c6d8903c94096c846
153 files changed