availability of a few timezones for "time_test" and "time_benchmark",
but (file-based) zoneinfo is now secured via existing Bazel data/env
attributes, or new CMake environment settings.

This also avoids the need for employing the CCTZ zone-info-source
extension mechanism (which is a win).

PiperOrigin-RevId: 488673952
Change-Id: I9def9d705c8f0dca3c0bcddc2406edb098ea5da3