Default clone candidate priorities are outdated

[mslw]

The default subdataset source candidate priorities listed in 101-148-clonepriority have changed since the time of writing. What's more, I feel that DataLad itself has an unintended interaction when assigning those. Relevant DataLad issues:

• Documentation for datalad.get.subdataset-source-candidate option gives an incorrect property for URL of a configured remote datalad/datalad#7458
• Subdataset source candidate cost inconsistent defaults datalad/datalad#7459

The priorities assigned by default can be 590 - 600 - 650 - 700 - 900, but I'm not 100% clear how to describe the rules (see issues above), so just an issue and not a PR for now.