Change to FlowModule to support the new flat flows
Change to FlowModule to support the new flat flows

This factors out a huge chunk of boilerplate that
would otherwise be in every single flow.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=133014837

google/nomulus,google/nomulus,google/nomulus,google/nomulus,google/nomulus,google/nomulus