[Binding SG] Add an API for creating instances of TypedBinding

[simonrozsival]

Description of Change

We recently enabled a source generator that allows developers to call the SetBinding extension method to define bindings on their bindable objects using Func instead of string paths. This PR builds on top of that feature and adds a second supported API that will not only set the binding directly to the object, but it will return the binding object instance and allow the developer to pass it to some other method and use it later.

Use-cases

1. Setters

Before:

maui/src/Controls/src/Core/Shell/BaseShellItem.cs

Lines 429 to 433 in 0572098

	BindingBase automationIdBinding = TypedBinding.ForSingleNestingLevel(
	nameof(Element.AutomationId),
	static (Element element) => element.AutomationId,
	static (element, val) => element.AutomationId = val);
	defaultGridClass.Setters.Add(new Setter { Property = Element.AutomationIdProperty, Value = automationIdBinding });

After:

BindingBase automationIdBinding = Binding.Create(static (Element element) => element.AutomationId); 
defaultGridClass.Setters.Add(new Setter { Property = Element.AutomationIdProperty, Value = automationIdBinding });

2. DataTrigger:

Before:

maui/src/Compatibility/ControlGallery/src/Issues.Shared/Bugzilla57910.cs

Lines 60 to 61 in c564156

	DataTrigger newDataTrigger = new DataTrigger(typeof(ProgressBar)) { Binding = new Binding(nameof(ListItemViewModel.State)), Value = ListItemViewModel.InstallableState.Downloading };
	newDataTrigger.Setters.Add(new Setter { Property = ProgressBar.IsVisibleProperty, Value = true });

After:

DataTrigger newDataTrigger = new DataTrigger(typeof(ProgressBar))
{
    Binding = Binding.Create(static (ListItemViewModel vm) => vm.State),
    Value = ListItemViewModel.InstallableState.Downloading,
};
newDataTrigger.Setters.Add(new Setter { Property = ProgressBar.IsVisibleProperty, Value = true });

3. MultiBinding

Before:

maui/src/Controls/tests/Core.UnitTests/MultiBindingTests.cs

Lines 68 to 78 in c564156

	entry1.SetBinding(Entry.TextProperty,
	new MultiBinding
	{
	Bindings = new Collection<BindingBase>
	{
	new Binding(nameof(Entry.FontFamily), source: RelativeBindingSource.Self),
	new Binding(nameof(Entry.FontSize), source: RelativeBindingSource.Self),
	new Binding(nameof(Entry.FontAttributes), source: RelativeBindingSource.Self),
	},
	Converter = new StringConcatenationConverter()
	});

After:

 entry1.SetBinding(Entry.TextProperty, 
 	new MultiBinding 
 	{ 
 		Bindings = new Collection<BindingBase> 
 		{ 
 			Binding.Create(static (Entry entry) => entry.FontFamily, source: RelativeBindingSource.Self), 
 			Binding.Create(static (Entry entry) => entry.FontSize, source: RelativeBindingSource.Self), 
 			Binding.Create(static (Entry entry) => entry.FontAttributes, source: RelativeBindingSource.Self), 
 		},
 		Converter = new StringConcatenationConverter() 
 	}); 

Issues Fixed

Contributes to #22384

/cc @jkurdek @StephaneDelcroix @jonathanpeppers

[jonathanpeppers]

@StephaneDelcroix what do you think about just putting the method here on Binding?

[jonathanpeppers]

I reran some tests, as I think the Xcode provisionator failures are fixed now.

[jonathanpeppers]

Seems like there might be mixed tabs/spaces in this file.

[StephaneDelcroix]

Having a Binding.Create() method allows the capture of the binding, and potentially a reuse of it, which isn't supported. I would stick with SetBinding...

[jonathanpeppers]

@StephaneDelcroix I think the three examples are Setter, DataTrigger, and MultiBinding (see description). I don't think you can use these APIs with data-binding on NativeAOT without an API that creates a BindingBase?