topoelementarray_agg that takes topogeom

[robe]

When you want to pass in a topogeom as a topoelement for building, the syntax is pretty ugly and hard to explain.

As discussed in this thread ​https://lists.osgeo.org/pipermail/postgis-users/2023-February/045845.html

In order to build hierarchical topoelement using topogeom, you need to do this ugly thing of

TopoElementArray_Agg( ARRAY[(topo).id,(topo).layer_id]::topology.topoelement )

It would be cleaner if we have a topoelementArray_agg that takes a topogeometry or have topogeometry be able to autocast to a topoelement.

Then the above would reduce to

TopoElementArray_Agg( topo )