Add support for Bzlmod for the next release

https://bazel.build/external/overview#bzlmod

Bzlmod will be the default in a future Bazel release.
By default it requires projects to be registered with the
Bazel Central Registry (https://registry.bazel.build/) and
thus uses regular releases by default.

Users that want to "live-at-head" can still do this through
with overrides (https://bazel.build/external/module#overrides).

This change updates GoogleTest dependencies to use released versions.
CI uses Bzlmod except in the case of linux_gcc-floor, which will
keep testing the old WORKSPACE-based dependency system.

PiperOrigin-RevId: 601489729
Change-Id: I6be52034eba0d0e5fe12110e5e82879305cf73ff

ci/macos-presubmit.sh

@@ -69,6 +69,7 @@ for absl in 0 1; do
     --copt="-Wundef" \
     --cxxopt="-std=c++14" \
     --define="absl=${absl}" \
+    --enable_bzlmod=true \
     --features=external_include_paths \
     --keep_going \
     --show_timestamps \