Updated data manager to handle no internet connection

[ZackAllen]

Description

The old data manager checks AGOL to create a portal item when verifying if offline data is present. This makes offline samples unusable offline. This PR fixes that behavior, so offline data that is already present on disk will load without an internet connection.

Type of change

• Bug fix

Platforms tested on:

• WPF .NET 6

• WPF Framework

• WinUI

• Xamarin.Forms Android

• Xamarin.Forms iOS

• Xamarin.Forms UWP

• UWP

• Xamarin.Android

• Xamarin.iOS

Checklist

• Runs and compiles on all active platforms
• Legacy platforms still compile and run (if applicable)
• Branch is up to date with the latest main/v.next
• All merge conflicts have been resolved
• Self-review of changes
• There are no warnings related to changes
• No unrelated changes have been made to any other code or project files
• sample_sync.py runs without making changes
• Codemaid and XAML styler extensions have been run on every changed file
• Code is commented with correct formatting
• All variable and method names are good and make sense
• There is no leftover commented code
• Screenshots are correct size and display in description tab