Parametrize all walls: Part 1

[Milopetilo]

Summary

None

Purpose of change

Use the palettes added in #77273 in order to have a bit more variation in walls.

Describe the solution

Look for every mapgen file that uses walls and apply the palette there. I've tried to avoid to change areas where the walls were chosen for specific reasons.

Describe alternatives you've considered

Not do this and stay sane.

Testing

Game loads, checked out some of the changed mapgen and it looks different.

Additional context

Might have merge conflict with #77287 but am unsure if it will.
This part has buildings with names starting from a-g, I'll try split up the next PRs in the same way.

[Maleclypse]

Do you mind making a PR that shows what parameters someone should use when adding new mapgen to the mapgen.md docs? Basically the goal is to avoid people having to come back and reparametrize new maps.