Port/move/create .NET samples

We're going to sunset the Xamarin samples, so we need to figure out what to do about .NET samples.

We've ported a few of our existing Xamarin samples to .NET in the `dotnet` branch in the `ios-samples` repository:

https://github.com/xamarin/ios-samples/commits/dotnet

Tasks:

* [x] Create a new `macios-samples` repository in the `dotnet` org. Coordinate with Android so we do don't things too differently.
* For reference, there's already a [dotnet/maui-samples](https://github.com/dotnet/maui-samples) repository.
* [ ] Update each .NET sample we have to the latest stable version of .NET (10 at the moment), and move into the new repository.
* [ ] Make sure the [sample browser](https://learn.microsoft.com/en-us/samples/browse/?expanded=dotnet) on Microsoft's documentation site lists these new samples.

Start by reviewing the existing .NET ports on the `dotnet` branch of the `ios-samples` repository and the task list in this issue. Compare the samples with the `dotnet/maui-samples` repository and coordinate with Android as noted. Done means the samples use .NET 10, are moved to `macios-samples`, and appear in Microsoft's sample browser.

Written by the indexing model from the issue text.