Fix VideoQuality.fromLabel to match higher resolutions first

[jamiepiccolo]

VideoQuality.fromLabel would give incorrect qualities in some cases.

An example being the 1440p label where the method would assign VideoQuality.low144 because of a premature match of the string's prefix "144":

if (label.startsWith('144')) {
    return VideoQuality.low144;
}

...

if (label.startsWith('1440')) {
    return VideoQuality.high1440;
}

I simply reversed the resolution map and looped over it so that we start matching from the highest resolution first.