Replace declarative_mixin with DeclarativeBase for all models

[bunchesofdonald]

This is the first in what is likely to be a long series of PRs that remove the models from the database abstraction layer. This PR:

• Makes the models use a DeclarativeBase instead of declarative_mixin.
• Updates many of the models files to use orm_models.<model> directly.
• Removes usages of PrefectDBInterface in filters and sorting.

Related to #11795

[chrisguidry]

Amazing! I did see some test suite snags but they mostly look like trivial call signature catchups after removing db.

[bunchesofdonald]

Thanks! I'll get those tests passing this morning.