feat: add handler method on menu item builders

[amrbashir]

closes #9060

[amrbashir]

This will leak the menu item and will never run the Drop implementation for it

[martpie]

Any news on this? Do you need help to test? :]

[amrbashir]

I haven't had time to work on this unfortunately, as this leaks the menu items and I haven't found a better design yet.

[dmgolembiowski]

I haven't had time to work on this unfortunately, as this leaks the menu items and I haven't found a better design yet.

Do you recall where you noticed the memory leak occurring?

[amrbashir]

The menu items are reference counted and it is expected to be either cloned by user or internally when added to a menu, both of which gives the user the ability to drop the item whenever feels like it.

However this PR implementation clones the item and moves it into a closure that is stored by tauri internals and so if the user drops all of his menu item instances, it is still kept around for the closure that is stored by tauri internals, hence the leak.

I am pretty sure it is not impossible, but I didn't have time to work on it lately.