Confirm exit without saving change in room details edit screen (#5618)

* Room details edit screen: add confirmation dialog when leaving without saving pending changes.

* Improve preview coverage.

* Update screenshots

* Introduce AsyncAction.ConfirmingCancellation and use it for leaving room edition without saving change.

* Fix issue in comment

* Use new `ConfirmingCancellation` object in Change Roles screen

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Co-authored-by: ElementBot <android@element.io>

libraries/architecture/src/main/kotlin/io/element/android/libraries/architecture/AsyncAction.kt

@@ -32,6 +32,11 @@ sealed interface AsyncAction<out T> {
 
     data object ConfirmingNoParams : Confirming
 
+    /**
+     * User cancels the action, use this object to ask for confirmation.
+     */
+    data object ConfirmingCancellation : Confirming
+
     /**
      * Represents an operation that is currently ongoing.
      */