Stop configuring lazy-loading for properties that will always be eager-loaded

[ajcvickers]

For example, for owner to owned navigation properties in aggregates.

See also #10787 (comment)

[lajones]

Notes from discussion with @ajcvickers and @smitpatel:

Define "properties that will always be eager loaded" as an INavigation (either reference or collection) which:

• has IsEagerLoaded == true
• has GetTargetType().IsOwned == true

In that case set up such that a) we do not need the virtual keyword, and b) check that attempting to lazy-load should be a no-op as we should already have eager-loaded.

[AndriySvyryd]

• has IsEagerLoaded == true

This isn't safe as we'll add an opt-out

[lajones]

@AndriySvyryd @smitpatel What would be safe?

[AndriySvyryd]

@lajones

• navigation.ForeignKey.IsOwnership == true for tracked enitites
• navigation.ForeignKey.IsOwnership == true && navigation.IsOnDependent == false for not tracked

[lajones]

We don't know whether the entity is being tracked at model validation time (which is when the current error is thrown). After more discussion with @AndriySvyryd and @ajcvickers we'll do something like:

if (navigation.ForeignKey.IsOwnership)
{
    if (!navigation.IsOnDependent)
    {
        // no-op (do not throw and do not warn)
    }
    else
    {
        // do not throw - this will be eager loaded
    }
}
else
{
    // throw as normal
}