Make DbContext release references to entities when they are removed or detached.

[Camel-RD]

Currently EF Core isn't releasing references when entities are removed from the context or detached. It probably doesn't matter when the context is recreated for each small unit of work, but in a winforms application, it would be preferable not to have to recreate the context every time some data needs to be reloaded. Before reloading data into DbSet I tried to clear it by setting the state Detached, but it doesn't work, memory isn't freed.