form: tab field layout improvements

Add some small improvements to the tab field:

- See if we can remove the custom condition in`FieldTemplate.jsx`'s render method
- Check if the style in `WrapIfAdditional.jsx`:44 is needed
- Change `TabField.jsx` so that either:
- The tab sider is replaced by a select field when the width of the parent component (as opposed to the screen size that we are using now) is smaller than a threshold
- Or modify our tab implementation so that nested tabs are displayed in the antd way, that is, as an expandable entry in the tabs sider that reveals the nested tabs in the sider itself with some indentation. Might be tricky in case we have a tab that inside has a normal field and another tab field (how do we display that normal field? the expandable item is not a tab by itself in antd, just a wrapper, and I don't know if it can be converted into one).
- A third option is to support both: the second option in case we have a tab with only another tab field inside and the first one in case there is a tab field together with other items