Fix #10059: Clamp config item values to int, disallow negative random deviation, and allow values up to 12 digits including '-'

[SamuXarick]

Motivation / Problem

We can't input custom negative values via query string on a config item and it can't be more than 10 digits.
Crash report is caused by implicit 64 bit to 32 bit conversions during construction of a script's settings.
We can't create labels for settings with a negative value.

Description

• Clamp config item values to int32. They're already correctly read as int64 (or SQInteger).
• Disallow negative random_deviation. It would cause weirdness during AddDeviation, because it expects uint. If it is negative, the abs of it is set instead.
• Allow custom values via query string to be negative and up to 12 digits, to allow for a large enough number, like -2 147 483 648.
• Also allow saving to the savegame and openttd.cfg numbers these large.
• AddLabels now checks the second character of key_string identifiers. If it finds a '_', then the integer that comes after becomes negative, allowing adding labels to negative values of a setting.

Limitations

I suppose none.

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 touches english.txt or translations? Check the guidelines
• 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

[glx22]

Documentation should mention the clamping and the allowed range.

[glx22]

Didn't check all documentation, but some places use MIN(int32) .. MAX(int32) style.
Not sure which one is better, but consistency is good.

[rubidium42]

First of all the commit message is not correct compared to this code. The 12 in here contains a trailing \0, so at most 11 digits could be placed.
Secondly, the whole function is trying hard to stay within the artificial 1024 byte limit, but then returns a theoreticall unbounded string, so why not use proper C++ constructs to create this settings string?
Thirdly, the ini file reading seems to use a 1024 byte buffer as well, so how can the written value ever be correctly read, because I think there is some key in front of the configuration.

So all-in-all it's more broken than this commit fixes, though I can agree that the second and third issue are not for this PR. The commit message definitely is broken, and the current number is magic-y without any comments, so what about something like:
char no[10 + 1 + 1]; // Maximum of 10 digits for MIN/MAX_INT32, 1 for the sign and 1 for '\0'.
And if the "12" gets used in many more places, a constant would be better as it can be reused, maybe something like INT32_DIGITS_WITH_SIGN_AND_TERMINATION.

[SamuXarick]

I placed INT32_DIGITS_WITH_SIGN_AND_TERMINATION in the script_config.hpp with comment, added includes in script_gui.cpp and game_gui.cpp to read this value. Also edited 2 commit messages.