Support ExecuteUpdate inside structural collections mapped to JSON

```c#
[ConditionalFact]
public virtual async Task Update_inside_structural_collection()
{
var nested = Fixture.Data.RootEntities.Single(e => e.Id == 1).RequiredRelated.NestedCollection[1];
nested.String += " Updated";

await AssertUpdate(
ss => ss.Set().Where(e => e.RequiredRelated.NestedCollection.Count >= 2),
c => c,
s => s.SetProperty(x => x.RequiredRelated.NestedCollection[1], nested),
rowsAffectedCount: 7);
}
```