Resolve "Change the ApiRetry wrapper to optionally handle 500 errors too"

Why is this change being made?

We want to expand the scope of ApiRetry wrapper to handle some additional 500 errors and other classes of errors that can be retried, as per #10122 (closed).

This also adds some spec coverage for the changes, and moves the ApiRetry module into a higher level directory since it's used elsewhere.

I don't think this will resolve all of the errors we hoped to catch, but it should catch a few. It also uses a (very simplified) exponential backoff algorithm, so we get some time between retries.

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Closes #10122 (closed)