[Feature Request] Use GeoPackage instead of Shapefile

[esnyder-rve]

SAGA supports geopackages (at least the GUI does), so it's weird to me that everything is done via shapefiles for vector formats with processing.

Context:
I ran into an issue when I needed to chain a bunch of Polygon Identity tools together. The output ended up having field errors due to the number of similar field names and the shapefile limitations. This made me have to go a different route for my model.

[cpWWS]

I also noted this issue when running gridding (natural neighbour). The input file (gpkg) has over 200 million points, and the program seems to convert it to a temporary shapefile before starting - is this really needed? perhaps a feature that could be improved in the future.

Also, the code (Natural Neighbour) on this large grid takes hours to run (about 12k x 12 k cells, so far 12 hours and it is not yet done...). it would be very useful to see more info on the log panel - 100% done but no messages and no output file... (image below)

My computer has 128 Gb of ram and a cpu with 20 cores. Only one core appears to be used in the process.

[baswein]

Adding this reference to an old QGIS issue with some details for reference. qgis/QGIS#47100