Coastal mask and update stac version

[FlorisCalkoen]

• coastal-mask stac
• set StacIO to default StacIO.default() instead of the customized class that we previously used. In the customized class we fixed windows paths, but that should be fixed by pystac now that we use pystac=>1.8.
• Pystac=>1.8 returns n validated items from the validate_all() method, so the pytest validate.py() is adjusted
• the requirements are upgraded
• the CI now runs using Python 3.11