Describe your issue or idea

When deleting a field, we see this message:

If you have any content left in this field, it will be lost. This action cannot be undone.

This always makes me a little nervous, even when I'm pretty sure there is no content in the field. Actually even if I've checked the database directly to make sure there is none. This is an idea for feedback: can we check if there is any content in that field and tell the user whether there is or not instead of this broad brush approach?

It could be simply:

There is content in this field which will be lost. This action cannot be undone.

Or (for example) when deleting a field from the "Page" content type:

7 pages have content in this field which will be lost. This action cannot be undone.

GitHub Link: 
https://github.com/backdrop/backdrop-issues/issues/3262
GitHub Issue #: 
3262