feat(logs): log polling backs off when it doesn't receive results

[philnash]

Fixes #251

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[dkundel]

What happens if we back off and then lots of logs (more than one page) get generated between the next poll. It doesn't look like we would currently fetch those again is that correct?

[philnash]

In the serverless-api methods we don't expose the pagination, so I had to write a new function for this particular method (to avoid changing results and making a breaking change).

Might it be worth changing the list methods for the resources here to expose pagination so that external modules can choose one or multiple pages when they use this?