Centralize txOverrides somewhere

[shanefontaine]

Allow for txOverrides to be updated in a single location but applied in all packages (possibly). Or let each package handle on their own 🤔 .

Not sure the best way to do this, because there are some very specific issues, such as txs on L1 needing more gas only when going into Optimism and Arbitrum. Maybe default all functions use estimated gas and we can specify which functions/chain/bridge to update gas for? Seems odd.

Should also be able to handle gasPrices, similar to Polygon’s min 30 Gwei that isn’t enforced by the nodes…