feat: use elevation capture areas for hillshade capture areas

[amfage]

📣 Co-ordinate merge with release linz/topo-imagery#1494

Motivation

Use the capture-area.geojson file of the upstream data source, which will be, or has been (change in progress) created from the national DEM/DSM capture-dates.geojson files.

Modifications

Do not create footprints when creating hillshades.
Use the supplied_capture_area parameter to provide a capture area from the upstream data source.
The exception to this are the merged DEM hillshades, which backfill from the 8m DEM and do not use the hillshade command. These will generate footprints as usual.

Note that if the 8m DEM needs to be recreated, create_capture_area will need to be set to true

Verification

Test workflows run.

[paulfouquet]

Is there any reason not changing create_capture_area to false for cron-national-merged-dem-hillshades, or is that forgotten? - I should have read the description :D