[Feature]: Enable support for Outfitter gear sets

[Gnathach]

Describe the feature

Would love if the category/sorting for Outfitter gear sets could be added. Outfitter has been maintained as a forked project for a few years now and AdiBags had a plugin called AdiBags_Outfitter that added categories for gearsets from it.

Describe the implementation

It could be done natively in BetterBags or as a plugin module like the old AdiBags one (created by AdiBags author as far as I can tell). It would have BetterBags categories for full item sets and also the partial accessory sets that Outfitter can create. Category titles are the name of the gear or accessory set in Outfitter.

I'm not sure how the AdiBags module decided sorting, but in cases where the same gear is used in multiple gear sets, it would somehow pick just one to show it in. As an example if my main role is a healer but I have a polearm for feral/guardian it would pick one of those two gear sets to sort the weapon into when not equipped but I don't know what the logic was on it.