feat(css): Update the syntax for `background-*`

[skyclouds2001]

Description

for background, simply the syntax to match the spec for <final-bg-layer> & <bg-image>, adjust order to match the spec for <bg-size>, update range value support, to be consistent with the spec

Motivation

Additional details

https://developer.mozilla.org/en-US/docs/Web/CSS/background https://drafts.csswg.org/css-backgrounds/#propdef-background https://drafts.csswg.org/css-backgrounds/#typedef-bg-layer https://drafts.csswg.org/css-backgrounds/#typedef-final-bg-layer https://drafts.csswg.org/css-backgrounds/#typedef-bg-image

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