SwiftUI timeline refactor + TimelineViewState decoupling (#1392)

* swiftUI conversion + scroll to bottom

* remove unused

* back pagination implemented, however when a lot of elements are in the scroll the perfomance diminishes not sure what may be causing it

* scroll adapter solution

* way better

* works but height animation in cells are broken

* code improvement

* everything implemented

* rebase fix

* fix

* doc

* fix test compilation

* code improvement and animation improvement

* code improvement

* code improvements

* tests updated.

* pr comments

* better identifiers

* fix

* some PR comments

* pr comments

ElementX/Sources/Other/ScrollViewAdapter.swift

@@ -29,7 +29,9 @@ class ScrollViewAdapter: NSObject, UIScrollViewDelegate {
             scrollView?.delegate = self
         }
     }
-    
+
+    var shouldScrollToTopClosure: ((UIScrollView) -> Bool)?
+
     private let didScrollSubject = PassthroughSubject<Void, Never>()
     var didScroll: AnyPublisher<Void, Never> {
         didScrollSubject.eraseToAnyPublisher()
@@ -73,6 +75,14 @@ class ScrollViewAdapter: NSObject, UIScrollViewDelegate {
     func scrollViewDidScrollToTop(_ scrollView: UIScrollView) {
         updateDidScroll(scrollView)
     }
+
+    func scrollViewShouldScrollToTop(_ scrollView: UIScrollView) -> Bool {
+        guard let shouldScrollToTopClosure else {
+            // Default behaviour
+            return true
+        }
+        return shouldScrollToTopClosure(scrollView)
+    }
     
     // MARK: - Private