fix: maxFeePerGas cannot be less than maxPriorityFeePerGas

[Reinis-FRP]

Motivation

GasEstimator is using hardcoded maxPriorityFeePerGas for some of networks. This can cause errors if estimated maxFeePerGas gets below this.

Summary

Enforce that maxFeePerGas is not set below maxPriorityFeePerGas.

Details

We experienced the error recently on Polygon where estimated maxFeePerGas got below hardcoded 50 GWei maxPriorityFeePerGas

Testing

Check a box to describe how you tested these changes and list the steps for reviewers to test.

• [ ] Ran end-to-end test, running the code as in production
• [ ] New unit tests created
• [x] Existing tests adequate, no new tests required
• [ ] All existing tests pass
• [ ] Untested

Issue(s)

Fixes #XXXX