Consider adding preset for waterway=soakhole and/or waterway=stream_end

[tyrasd]

Continued from https://github.com/openstreetmap/id-tagging-schema/pull/1233/files#r1667361443:

The tag natural=sinkhole is currently commonly used to mark places where waterways end by percolating underground. This use does not really match the tag's documented definition. Unfortunately, the alternative tag waterway=soakhole is not established outside of an import in New Zealand: see the distribution of the tag's usage.

[k-yle]

waterway=soakhole has an identical definition to waterway=stream_end.

waterway=stream_end has seen organic growth, while waterway=soakhole is almost entirely from the LINZ import.

I recently proposed changing the imported nodes to use the more popular tagg, but there was some opposition...

So I don't think we can create a preset while there still 2 tags with the same meaning