[11.x] Add inCents parameter to Number::currency helper

[rtrudel]

This pull request adds an inCents parameter to the Number::currency method, allowing us to specify whether the $number parameter is in cents. This makes it easier to format currency values without having to convert them beforehand.

As Stripe and many other payment gateways use cents-based amounts for prices, this addition simplifies the display of prices in applications.

Before:

// With a price of 1500 cents from Stripe
$price = $stripePrice / 100;
Number::currency($price); // outputs "$15.00"

After:

// With a price of 1500 cents from Stripe
Number::currency($stripePrice, inCents: true); // outputs "$15.00"