Remove: [Script] CONFIG_RANDOM from AddSetting flags (#11942)

It had a very weird interaction, and was only ever used by a single
AI.

Fix #10059: [Script] Clamp config item values to int32

Also prevent random_deviation to be below 0.

Codechange: move casting a "const char *" to "char *" to the caller

It is not nice to have your definition say you won't change a value
while in fact the whole reason for your existance is to change it.

Codechange: rename str_validate to StrMakeValid(InPlace) (#9304)

This to be more explicit the function changes the value, and not
returns yes/no.