Final updates to tutorial series for 8.0

[adegeo]

Tutorial 1:

• Added links to download a zip of the code at end of the first tutorial.
• Removed "browse code" and "download code" from the the interim steps.
• Recrafted the code from scratch using the latest .NET 8 template.
• Added a screenshot showing visual studio's collapsing xaml file.
• Reshot all device\app screenshots.
• Split the final tutorial step into two steps.

Tutorial 2:

• Removed the upgrade page.
• Added links to download a zip of the code to the start and end of the second tutorial.
• Removed "browse code" and "download code" from the the interim steps.
• Recrafted the code from scratch using the latest .NET 8 template.

Depends on dotnet/maui-samples#450 -- Merged
Depends on dotnet/maui-samples#453

Fixes #1848
Fixes #2034

[davidbritch]

Approving so you're unblocked, but a couple of things that need fixing.