Add option to customize the Settings navbar

Platform: Brave 1.77.0 on Windows 10 Home x64 22H2

For those not interested in Brave Rewards or BAT points, offer a customize option to remove “Rewards” from the navbar (header) at the top of the Settings page.

Same for adding a customize option to remove the “Wallet” from the navbar in Settings.

For users that will never use rewards or a wallet, their appearance in the Settings navbar is both superfluous and distracting. Rather than bury these navbar customization settings in the general settings, add a gear icon to the Settings navbar that lets the user decide just what to show in the navbar. Probably the only item in the navbar that should not be removable is Settings itself.