Unified Codebase for Retail, Classic, and TBC

[Cidan]

This CL resolves #646 and fully unifies the codebase for all three versions of World of Warcraft on the market. It works by adding 4 new constants to Constants.lua that can determine the running version at runtime. These constants are then used to conditionally branch various parts of the code so AdiBags works across all three releases from a single codebase.

This CL also adds support for building all three versions via BigWigsMods packager under a single git tag. At any point after this CL, simply upload a new tag and the Github action tied to this repo will build the correct artifacts for each version of WoW.

Things to note:

• Some parts of the code that are "dead" and unused are not conditionally escaped for classic. This is intentional and harmless, as the code is never actually run, and there's no use in escaping it
• Only code that is actively executed by WoW and needs to be changed has been modified
• The config screen still needs a few changes for classic, i.e. there are still references to glyphs
• This has not been tested with the coming WotLK release, but will be addressed when pre-patch is released with the new API's

I've tested on retail, classic, and classic era:

• Bags
• Filters
• Bank Bags
• Reagent Bags
• Void Storage

I've encountered no obvious bugs. @Talyrius Can you do a quick lookover and see if this looks good? I know you're not around much, which is fine -- if I don't hear from you by sometime next week, I'll go ahead and merge this.

Thanks!

[Cidan]

If you have no comments, I'm going to merge this so I can get started on the current open issues. Unrelated, but thanks with the help triaging the older issues that needed to be resurfaced @Talyrius :)

[Talyrius]

Other than some whitespace nitpicks (unimportant as the rest of the codebase is inconsistent as it is), nothing stands out to me. I haven't yet reactivated my sub to test drive it, but you said you had already done so anyway. Looks good! 👍

[Cidan]

Awesome, I'll merge this later tonight!

re: Whitespace, I'm thinking about adding some linting rules to fix this in general. I'll revisit it.