Copies text, tags, and paintables between start and end and inserts the copy at iter.
The order of start and end doesn’t matter.
Used instead of simply getting/inserting text because it preserves images and tags. If start and end are in a
different buffer from this, the two buffers must share the same tag table.
Implemented via emissions of the insert_text and apply_tag signals, so expect those.
| this |
a `GtkTextBuffer` |
| iter |
a position in this |
| start |
a position in a `GtkTextBuffer` |
| end |
another position in the same buffer as |