Revert #11993: new number format system does not and cannot work for CJK languages

There are too many intricacies that I am unaware of that are popping up after
asking whether things are right or not.
I do not want to keep playing whack-a-mole, so just revert the whole thing.

This reverts:
15be383b934dbf7c876b6d6ffaec7a406c82a39f
360fe8b0b639be9d39bc03a9d5d34123204c14fa
1aa9a5c0abaf9c5d6c49a3a76e2b1d7134c0bd10
59f56941e50bd4ebad31f9e771a4441f647692e5
7e2eefb91ff5999667752eea6e13bd8a0d293f48
b741b2ba6f790891961cb66a9320e75ca168cee4
609d0071d5e6b93aa61688714e9b92cf102e4683
9f8fd80112c188675179c9568a9be84da3df1713
a253205b932cc50fc9f25be390a6aaa370f89a45
819c6c756edd68599571eae126f305d6e3d247fc

Codechange: automatic adding of _t to (u)int types, and WChar to char32_t

for i in `find src -type f|grep -v 3rdparty/fmt|grep -v 3rdparty/catch2|grep -v 3rdparty/opengl|grep -v stdafx.h`; do sed 's/uint16& /uint16 \&/g;s/int8\([ >*),;[]\)/int8_t\1/g;s/int16\([ >*),;[]\)/int16_t\1/g;s/int32\([ >*),;[]\)/int32_t\1/g;s/int64\([ >*),;[]\)/int64_t\1/g;s/ uint32(/ uint32_t(/g;s/_uint8_t/_uint8/;s/Uint8_t/Uint8/;s/ft_int64_t/ft_int64/g;s/uint64$/uint64_t/;s/WChar/char32_t/g;s/char32_t char32_t/char32_t WChar/' -i $i; done

Change: treat languages as finished, if translations are 75% completed.
Unfinished translations are not auto-picked from the locale.
In release builds, unfinished translations are not offered in the GUI.
Unfinished translations are available in non-release builds, or by editing openttd.cfg.

Codechange: ICU_SORT is in reality ICU_I18N (according to their CMake files)

By naming it in a different way, things get a bit confusing.
Especially if we are switching to CMake, which autodetects these
things, we need to use the name the authors of ICU gave it; not
our interpertation of that name.