Improve Link Preview Sizing

Update linkpreviewer to minimise the number of resizes.

- There is now a placeholder loading element to hold space while the data is obtained
- The component starts with a set size but can be expanded to see the whole item.
- The expand/contract button is only visible on hover
- The default size is picked to show 3 lines of text (1 heading and 2 description, 2 heading and 1 description, etc)

This is designed to help with the timeline scroll jumping CCBUG: 463235 by minimizing the amount of resizing for items in the timeline.

Before

![image](/uploads/bb46f55dc38851e640a7382aafea8640/image.png)

After when compressed

![image](/uploads/3cbc7894688721d944a5551251b12a12/image.png)

After When expanded

![image](/uploads/50ff53fe51eefe88713a2ded34530534/image.png)

After Loading

![image](/uploads/72567f805af6b08ab0c5fc1cf94bd247/image.png)

src/qml/Component/Timeline/MessageDelegate.qml

@@ -29,14 +29,8 @@ TimelineContainer {
             messageId: model.eventId
             visible: currentRoom.chatBoxEditId === model.eventId
         }
-        Loader {
-            id: linkPreviewLoader
+        LinkPreviewDelegate {
             Layout.fillWidth: true
-            active: !currentRoom.usesEncryption && model.display && model.display.includes("http")
-            visible: Config.showLinkPreview && active
-            sourceComponent: LinkPreviewDelegate {
-                anchors.verticalCenter: parent.verticalCenter
-            }
         }
     }
 }