[Fix] Change on-demand resources downloaded state criteria

[yo1995]

Description

This PR fixes the ODR resource force unwrap not found problem described in #48

Linked Issue(s)

• swift/issues/4199

How To Test

1. Do a fresh install and fresh build
2. When the samples app first open, check an arbitrary sample that has ODR, e.g.
   • Add raster from file
   • Add feature layers
   • Change camera controller
   • Display map from mobile map package
3. Make sure none of them crashes

To Discuss

I haven't been able to reproduce a crash with this fix. My gut says the root cause was that when NSBundleResourceRequest sets its progress to 100%, it is not immediately setting the isResourceAvailable to true, or it is dispatched onto the main serial queue whereas the state change is propagated to the view earlier than that. 🧐

• One way to fix is to move the requestState = .downloaded to a later point.

According to the doc for beginAccessingResources(completionHandler:),

The resources are not available until the completion handler is called with error set to nil.

So when the try await request.beginAccessingResources() call returns, the resource must be available.

• Another potential way to fix is to call the download() method again after the progress reported 100%, so it conditionally checks for the resource again.

[dfeinzimer]

I was unable to produce a crash on v.next to validate but was unable. Changes look okay.

[yo1995]

Thank you! I was able to crash twice on v.next with random order of accessing these ODR samples in about 10 fresh installations, and haven't crashed yet with the fix. Will merge and keep an eye on any future crashes if there is any. 👀