Switch Retry Algorithm to Exponential Backoff

[sdtsui]

(This issue uses private Slack archive links.)

From @maurycyp in Slack: we'd like to lower our total number of retries for pending tx's, using exponential backoff. This would decrease load on infura nodes, and help lower current congestion more quickly. This was discussed live with @frankiebee and is ready to be started on.

There are a few libs out there that can help with this. It may be simplest to roll our own algo, using examples here and here: just remember to cap the backoff to, say, a day. I'm not familiar enough with these controllers to suggest that we use localStorage to keep track of retries or if we have a preferred way of doing this: will leave it up to the implementor.

• Potential (i.e. suggested) place for this change: transactions.js. Looks like retryCount is already implemented.
• Additional context: how this change will be used in pending-tx-tracker: here & here.

Notes:

• MetaMask and Infura will discuss this morning, when more of the team is awake.
• In parallel, Frankie may be able to work on disabling/tweaking manual resubmit.

[danfinlay]

Cool idea!

[sdtsui]

Implemented in #2670.