Remove furniture/terrain legacy alias code and JSON

[ShnitzelX2]

Summary

Infrastructure "remove furniture/terrain legacy alias code and JSON"

Purpose of change

This is roughly half of #73211, which indeed turned out to have too many issues to rebase completely. From that PR, the rationale: "Removes remaining redundant aliases and alias code".

This work was done by @Procyonae, I just isolated the changes and cleaned them up.

Describe the solution

I mostly solved merge conflicts, and I made sure that any remaining "alias" fields don't exist in the "json" or "mods" directories.

I'm aware of #77459 and made sure to rebase over it; there weren't any serious conflicts.

Describe alternatives you've considered

Doing this from scratch would require a lot more work, I think.

Testing

• clang-tidy, astyle, JSON formatted locally
• Passed all tests locally
• Made sure the game loads without JSON errors for all affected mods
• Checked most of the particularly conflict-heavy mapgen, including: abandoned_shopping_plaza, DinoMod's zoo, GM_LODGE_PALETTE, NoHope's necropolis

Additional context

Additional thanks to @Procyonae for doing the original work

[RedMisao]

Question: What was alias for ?

[PatrikLundell]

@RedMisao:
In at least some cases aliases are used to specify orientation:

   "id": "t_chainfence",
    "alias": [ "t_chainfence_h", "t_chainfence_v" ],

however, I have no idea if it's actually used for anything, but suspect it was once used for display purposes but now replaced by logic to connect likes (this is a guess, not a fact in any way) to sort out how to display it.

[ShnitzelX2]

That's the gist of it, yeah. From what I've read, aliases were made (about 8 years ago in #16368) to replace a table converting _h/_v variants of tiles into a parent tile during mapgen, and connect groups were also built to display aliased tiles correctly.

The bottom line is that _h/_v tiles are unnecessary legacy mapgen and have been for a long time -- they were called legacy in #14585! Connect groups further make aliases unnecessary, too.