Someone may @Inject a Random at some point in the future where security matters,
so always provide a secure one.
Also, this shouldn't be in ConfigModule (it's not configuration) -- but that can
be changed separately. We might want a larger refactor that has a utils module
or similar to provide extremely generic things like random number generators.
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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=217602486