Add DA.Text.isNotEmpty function

[wallacekelly-da]

A Text.isNotEmpty function is needed frequently enough to warrant being added to the standard library.

Some might say that a Text.isNotEmpty function is not necessary. It is true that Daml developers today can add their own definition of isNotEmpty whenever necessary. However, the same could be said of a Text.isEmpty function. We have a Text.isEmpty function in the standard library because a Text.isEmpty function is needed frequently enough to warrant being added. The same is true for Text.isNotEmpty.

This was discussed in the Daml forums.