[feat] Upgrade material-ui library to v5

[roshaans]

Update the app to use MUI v5 instead of v4. This will allow us to use the LoadingSpinner.

This will require us to create a custom theming class which overwrites default look of the components in MUIv5 but may be beneficial to us as we can have a light/dark mode option.

loading button specs

• Can we use the material ui loading/spinner button for loading state vs a custom sendingString? We've been meaning to do that in the wallet too since it's more standard than switching out the button text while loading - Posted by @Patrick1904