Code Quality: Upgrade from `H.Generators.DependencyPropertyGenerator` to Toolkit Labs DP generator

[Lamparter]

Description

The current DP generator isn't as good as the new one from Toolkit Labs.
We should migrate to using that one instead as it will improve all sorts of things, and allow the removal of the HAS_$(MultiTarget.ToUpper()) constant to improve compilation.

Concerned code

• Riverside.Toolkit.WinUI.Controls: This is used by TitleBarEx

Gains

• Removal of unnecessary constant
• One of the first customers of the Toolkit Labs DP generator!

Requirements

• Examine documentation
• Speak to Sergio
• Replace DP generator
• Replace references to DPAttribute

Comments

No response