Implement `[BindableProperty]` for ValidationBehaviors

[TheCodeTraveler]

Description of Change

Note: This PR is in draft as MultiValidationBehavior requires an Attached Bindable Property (eg BindableProperty.CreateAttached()).

This PR implements [BindableProperty] for Validation Behaviors.

PR Checklist

• [x] Has tests (if omitted, state reason in description)
• [x] Has samples (if omitted, state reason in description)
• [x] Rebased on top of main at time of PR
• [x] Changes adhere to coding standard