Bug 1909462 - Switch requestAnimationFrame handles to be uint32_t per spec. r=webidl,emilio

The current version of the spec indicates that we should be using
uint32_t instead of int32_t for the handles with requestAnimationFrame
and cancelAnimationFrame.

https://html.spec.whatwg.org/multipage/imagebitmap-and-animations.html#animation-frames

Differential Revision: https://phabricator.services.mozilla.com/D217427