Text cursor at end of text cannot be textured separately from underscore character (_)

The bug

The text cursor version used at the end of a string of text will always use the same texture assigned to the underscote character. It is not at all possible to customize it differently.

How to reproduce

A resource pack is attached that demonstrates this by retexturing the underscore.

How to fix

Introduce a separate, dedicated texture file for this text cursor.

Further notes

Until recent versions, it appears that the text cursor for when between characters was tied to the vertical bar character |. This is no longer the case, but to my knowledge it still cannot be retextured.