[Perf] Avoid the materialization of list of handlers when raising events

[dr1rrb]

What would you like to be added

When we raise routed events args, we are creating a new array (not even pooled!) which contains the list of all event handlers for the given event:

uno/src/Uno.UI/UI/Xaml/UIElement.RoutedEvents.cs

Line 693 in 1d71b1b

foreach (var handler in handlers.ToArray())

. This can be a hot-path and can be really expensive for nothing, we can improve this in multiple ways:

• Most of the time we will probably have only one handler. In such case no needs enumerate the handlers collection!
• The clone is made to allow the removal of an handler during the enumeration. This is not the common scenario, we could imagine to have a dedicated collection implementation that will clone the collection only if an element is being removed during enumeration / effectively removes the element only once enumeration is completed / ...

Why is this needed

No response

For which platform

No response

Anything else we need to know?

No response

[Youssef1313]

The clone is made to allow the removal of an handler during the enumeration. This is not the common scenario, we could imagine to have a dedicated collection implementation that will clone the collection only if an element is being removed during enumeration / effectively removes the element only once enumeration is completed / ...

I attempted a quite similar thing in #14069