Ingest 3rd party gas oracles for retry strategies

[KPrasch]

This is a replacement for PR nucypher/nucypher#3412

The general idea of this issue, is to query 3rd party APIs (like etherscan, polygonscan, etc.) to improve the efficiency, robustness and success rate of transaction retry strategies.

This issue can be closed by a PR that integrates a configurable mechanism that works with popular gas/price oracles, documented usage examples ("cookbook" style), or by decision that such functionality is too domain-specific.

[cygnusv]

We have evidence that Infura is sometimes not providing correct max priority fee estimates (at least on Polygon Mainnet), which can affect TX finality; in particular, they often suggest fess below 30 gwei, which in theory is the minimum. Using gas price feeds together with our own validation rules can help.