Support setting a custom gas limit and gas price

[john-light]

It can often happen, especially on less-used networks or with newer contracts, that the default gas limit presented to the wallet for signing will result in an out of gas error, or on the other end, is way too high and gives the user an artificially-inflated expectation regarding the price of their transaction (or, it causes them to think the cost exceeds their gas balance).

Additionally, there are scenarios where users want more control over gas prices, such as during high-stakes trades or mints. It would be nice to give users this advanced level of control in the gas settings section.

Mockup: