Prepare for Bazel incompatible changes

Fixes googletest for upcoming `--incompatible_load_cc_rules_from_bzl` (https://github.com/bazelbuild/bazel/issues/8743) and `--incompatible_load_python_rules_from_bzl` (https://github.com/bazelbuild/bazel/issues/9006).

This change was automatically generated with `buildifier -lint=fix -warnings=all $(find . -name "BUILD" -o -name "BUILD.bazel" -o -name "*.bzl")`.