load_disk_collection: deprecate/migrate to load_uploaded_files

[jdries]

load_disk_collection is backed by a process that is only supported on Geotrellis backend. There also do not seem to be unit tests.

Use cases of this method can probably be replaced by load_uploaded_files. This new process does not seem to support globs, but that's perhaps open for discussion in the process spec, it's still experimental anyway.

https://processes.openeo.org/draft/#load_uploaded_files

[jdries]

turns out that a lot of this is in place already, and we now have initial support that would allow us to already start avoiding load_disk_collection