This patch adds data about instances generated by geometry nodes to the spreadsheet.
The transform data is decomposed into position, rotation, and scale, and there is a
name column to display the name of the instanced object or collection.

This data is implemented specifically for the spreadsheet, because we're not sure
that we want to expose this data as attributes for the rest of geometry nodes.

The only remaining problem is that the index column is too narrow for some reason,
I'll need to spend a bit more time debugging that. Also, the icon might not be ideal.

A note for the future, eventually the instances data will also contain geometry sets instanced
directly in the node tree, and those likely won't have names.