Since this reporting is getting more complicated (see b/36599833), it'll
be better to have a dedicated class to encapsulate it, which also lets us
keep the tests separate and focus FlowRunner more on its core purpose of
actually running the flow.
Note that this doesn't move the legacy log statement logging because that
specifically must be logged from the FlowRunner.run() method to preserve
the existing log signature matching in our ICANN activity reporting query.
(The new statement is designed to be robust to moves like this since it
doesn't use the logging callsite to match log lines, and it's not in use
yet anyway.)
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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=153762008
