gas price adder & priority fee bugfix

[zeroXbrock]

Motivation

Was seeing a lot of "replacement transaction underpriced" errors.

Solution

Started by adding a mechanism to automatically increase the gas price when we saw the error. The spammer increased the gas price a ton yet I still saw the error, which led me to find an inconspicuous bug in the priority fee calculation.

With that fixed, gas price increases happened much less frequently. They still happen, though, so every time contender sees an "underpriced" error, it increases the gas price for following txs by 10%. When a batch of transactions is sent without error, the gas price for the following batch is decreased by 10%. This ensures we can keep running the spammer for a long time without the gas booster going exponential.

spamd now reliably fills blocks on a live testnet until the accounts run out of gas, at which point contender must be manually stopped.

Future improvement

In spamd, automatically replenish funds in agent accounts

PR Checklist

• Added Tests
• Added Documentation
• Breaking changes