#528 Change multiple selection color in batch

[thekingofcity]

More explanation on why batch operations should be done in color-field.tsx. ColorField is a convenient way for elements(nodes/stations/lines) to change their attributes in the Specific Attributes section. With this as the primary goal, it should only provide ways to change the attributes in that particular element. And no matter what the element contributor does, it should never touch attributes in other elements. The suggestion for the ColorField overhaul aligns with other <RmgFields /> by requiring only currentTheme and handleColorChange. When using, it should look like the following:

const someStationAttrsComponents = (props: AttrsProps<SomeBasicStationAttributes>) => {
    const { id, attrs, handleAttrsUpdate } = props;
    const { t } = useTranslation();

    const fields: RmgFieldsField[] = [
        {
            type: 'custom',
            label: t('color'),
            component: (
                <ColorField
                    currentTheme={attrs.color}
                    handleColorChange={color => {
                        attrs.color = color;
                        handleAttrsUpdate(id, attrs);
                    }}
                />
            ),
        },
    ];

    return <RmgFields fields={fields} />;
};