Fix crash when deleting a row from @ObservedSectionedResults

[leemaguire]

Observing the sectioned results directly doesnt allow the SwiftUI diff to work correctly as the previous state of the sectioned results will have the new values.

An example of when this is an issue is when an item is deleted in a List containing sectioned results, the diff needs a stable state of the previous transaction but due to the observation callback calling calculate_sections the collection will be brought up to date.

The solution around this is to store a frozen copy of the sectioned results and observe the parent Results instead. Each time the results observation callback is invoked and the SwiftUI View is redrawn the sectioned results will be updated.

[dianaafanador3]

Suggested change

	* Add `@ObservedSectionedResults.remove(atOffsets:, section:)` which adds the ability to
	* Add `@ObservedSectionedResults.remove(atOffsets:section:)` which adds the ability to

[dianaafanador3]

We could also add an append function, something like this

public func append(_ value: Value.Element.Element) where Value.Element.Element: Object {
        write(wrappedValue) { collection in
            collection.realm!.add(value)
        }
}

[dianaafanador3]

Users would be able to append objects to the collection used within @ObservedResultsSection without having a reference to the realm or having to thaw the realm from the wrappedValue

let reminderList = ReminderList()
$reminders.append(reminderList)

[dianaafanador3]

Suggested change

	Observing the sectioned results directly doesnt allow the SwiftUI diff to work
	Observing the sectioned results directly doesn't allow the SwiftUI diff to work

[dianaafanador3]

Do we really need to add an observation here as well and update the sectionedResults value if there is change in value in results, isn't the above code doing it already, it seems like you are duplicating updating sectionedResults

[dianaafanador3]

I tested this and seems to be making this workaround to work.

[GriffinMeyer]

Is there an ETA on this getting released? We'd love to be able to implement grouped lists!