Remove ArrayLists #8406
Description
This project still contains a lot of ArrayLists (quick search: https://github.com/search?q=repo%3Adotnet%2Fwpf%20arraylist&type=code ).
XPS: https://github.com/search?q=repo%3Adotnet%2Fwpf+ArrayList+xps+language%3AC%23&type=code&l=C%23
ArrayLists are not recommended and require a lot of boxing/unboxing (performance)
https://learn.microsoft.com/en-us/dotnet/api/system.collections.arraylist?view=net-7.0#remarks