Document temporal table non AsOf operations with navigations

Temporal table works best with AsOf operations - we can translate any query because there is a consistent graph of entities that matches what EF "thinks" entities should be. For other operations (e.g. TemporalAll) we get into all sorts of trouble leading to unexpected results (missing or mismatched rows)

As such, we disabled navigations for non-AsOf operations and we recommend people to manually build the queries they need using joins. These are quite tricky and not intuitive. We should provide some guidance and examples of how it can be done (by converting navigations to N+1 queries or swapping LEFT/INNER JOINS into CROSS JOINS)

Some examples of problems/queries users want to solve that we should consider documenting a solution for:

https://github.com/dotnet/efcore/issues/34384
https://github.com/dotnet/efcore/issues/34978