[ios/catalyst] fix memory leaks in ListView (#22007)

* [ios/catalyst] fix memory leaks in ListView

Fixes: #20025

I could reproduce the leak here, pretty easily with changes to `MemoryTests`.

`ListView` has several cycles that prevent garbage collection from
happening:

* `FormsUITableViewController` has `ListView _list`
    * `FormsUITableViewController` -> `ListView` -> `ListViewRenderer` -> `FormsUITableViewController`

* `ListViewDataSource` has `UITableView _uiTableView`
    * `ListViewDataSource` -> `UITableView` -> `ListViewDataSource`

* `ListViewDataSource` has `FormsUITableViewController _uiTableViewController`
    * `ListViewDataSource` -> `FormsUITableViewController` -> `UITableView` -> `ListViewDataSource`

* `ListViewDataSource` has `protected ListView List`
    * `ListViewDataSource` -> `ListView` -> `ListViewRenderer` -> `FormsUITableViewController` -> `UITableView` -> `ListViewDataSource`

I changed the above fields to all be `WeakReference<T>` and the leaks
went away.

* Tentative fix for Android

Context: #18757

* Revert "Tentative fix for Android"

This reverts commit b294779.

* Ignore ListView test on Android for now

Author: jonathanpeppers