Fixes #9386.

Motivation / Problem

MacOS build currently fails because our setting tables are too big. But we have been willing to split the settings table up for a while now. So a good enough reason to make that happen.

Description

This reduced the load on compilers, as currently for example MacOS
doesn't like the huge settings-tables.

Additionally, nobody can find settings, as the list is massive and
unordered. By splitting it, it becomes a little bit more sensible.

I split the settings based on the group they are in the settings. There is a lot more to do here, but I wanted to keep an easy-to-review PR. If you use a coloured-diff, you will see that things are only moved:

git fetch https://github.com/TrueBrain/OpenTTD settings-split-table
git show FETCH_HEAD --color-moved=zebra

settings.ini is removed completely, meaning patches will have a nice conflict on it, making it more clear for patches they should be moving their settings.

Future-PRs can address stuff like:

• Make flags default per settings-file and reduce the amount of things being repeated
• Force settings-files to read/write into a given struct (instead of repeating that every time)
• Move some settings around; there are some strange choices currently, for example I am not sure pf.reverse_at_signal should be a pathfinding setting. And there are more similar weird ones.
• Many more small things.

But, this PR is just to get that car moving. I will not be addressing these things above any time soon, so if you want to, feel free to go for it :)

Limitations

Checklist for review

Some things are not automated, and forgotten often. This list is a reminder for the reviewers.

• The bug fix is important enough to be backported? (label: 'backport requested')
• This PR affects the save game format? (label 'savegame upgrade')
• This PR affects the GS/AI API? (label 'needs review: Script API')
  • ai_changelog.hpp, gs_changelog.hpp need updating.
  • The compatibility wrappers (compat_*.nut) need updating.
• This PR affects the NewGRF API? (label 'needs review: NewGRF')
  • newgrf_debug_data.h may need updating.
  • PR must be added to API tracker