Block view title is not translated when displayed as a ds field

Getting close with this patch. To fix:

- Adding translation acts a bit weird, it overwrites the original initially as well (but does save the translated label)
- getting to use the translated version of the title in the frontend
- clear cache when adding/deleting ds field (to trigger ds_config_translation_info_alter()).

(this would have probably been easier and more logic if our fields were config entities, but oh well)

So ironically, if you use the title from the field itself, you can translate via the translate ui - cf DynamicField class. Completely missed that.

Adding t() around the title when it comes from a block or views is not my favorite option here, so simply closing.