Add ItemsTransitions for the SettingsExpander

[zhuxb711]

Better visual effect when some of the items visibility within SettingsExpander changed

Fixes

• None

PR Type

What kind of change does this PR introduce?

• Xaml style update for better children transition for SettingsExpander

What is the current behavior?

• No transition for items in SettingsExpander

What is the new behavior?

• With basic transition for items in SettingsExpander

PR Checklist

Please check if your PR fulfills the following requirements:

• Created a feature/dev branch in your fork (vs. submitting directly from a commit on main)
• Based off latest main branch of toolkit
• Tested code with current supported SDKs
• New component
  • Documentation has been added
  • Sample in sample app has been added
  • Analyzers are passing for documentation and samples
  • Icon has been created (if new sample) following the Thumbnail Style Guide and templates
• Tests for the changes have been added (if applicable)
• Header has been added to all new source files
• Contains NO breaking changes

Other information

[niels9001]

@zhuxb711 Can you help me understand what the proposed changes are and what issues it will fix? We need to make sure that these controls stay as closely aligned to what's currently in W11 Settings as possible.

[zhuxb711]

@niels9001 Add property ItemsTransitions could provide more smooth experience if the SettingsCard in the SettingsExpander will be dynamic changed.

To be honest, SettingsExpander have lots of limitation on the Items it can contains. And not that easy to migrate from my hand make custom settings controls. Which is more flexible to support any controls. For example, if I want to make something like the combination of SettingsExpander & SwitchPresenter, the only way is list them all in the SettingsExpander.Items and control their visibility one by one. However, no animation for the Items once visibility changed due to SettingsExpander have no children transitions all.

ItemsTransitions is a compromise solution. I think SettingsExpander should not assume that developer will only put SettingsCard in it. Even no document mentioned it. It just simply crashes with confusing information

With ItemsTransitions: