stakingFeeSat callback

[gbarkhatov]

Currently stakingFeeSat is a memoized function.
@jrwbabylonchain suggested we have a callback function

@jrwbabylonchain please add the details of:

• What it will improve
• Your suggestion about the function

[jrwbabylonlab]

What it will improve

Avoid the react re-rending issue. as explained here #252 (comment)

I have put a console.log("rerended") inside the stakingFee.tsx. When i hit the button to adjust the fee. i have this log printed 8 times in total. so 8 re-render.
Imaging if we have a api call here, then this would be an issue.

Your suggestion about the function

Highlighted here with examples: #252 (comment)