Codechange: use setting name instead of index for CmdChange(Company)Setting (#9306)

This is mostly done as there are now constraints on settings.ini you might not
expected. For example, conditional settings always have to come last, as otherwise
they would influence the index.

src/settings_func.h

@@ -32,7 +32,6 @@ struct GRFConfig *LoadGRFPresetFromConfig(const char *config_name);
 void SaveGRFPresetToConfig(const char *config_name, struct GRFConfig *config);
 void DeleteGRFPresetFromConfig(const char *config_name);
 
-uint GetCompanySettingIndex(const char *name);
 void SetDefaultCompanySettings(CompanyID cid);
 
 void SyncCompanySettings();