Put HAvatar's tooltip image inside a Loader

Make sure to not load tooltip images unless the user is
currently trying to see one by hovering on an avatar.
This also seems to reduce idle CPU usage.

src/gui/Base/HAvatar.qml

@@ -13,13 +13,13 @@ Rectangle {
     property alias clientUserId: avatarImage.clientUserId
     property alias mxc: avatarImage.mxc
     property alias title: avatarImage.title
-
-    property alias toolTipMxc: avatarToolTipImage.mxc
     property alias sourceOverride: avatarImage.sourceOverride
-    property alias toolTipSourceOverride: avatarToolTipImage.sourceOverride
     property alias fillMode: avatarImage.fillMode
     property alias animate: avatarImage.animate
 
+    property string toolTipMxc: mxc
+    property string toolTipSourceOverride: ""
+
     readonly property alias hovered: hoverHandler.hovered
     readonly property alias circleRadius: avatarImage.circleRadius
 
@@ -93,13 +93,17 @@ Rectangle {
             delay: 1000
             backgroundColor: theme.controls.avatar.hoveredImage.background
 
-            contentItem: HMxcImage {
+            contentItem: HLoader {
+                active: avatarToolTip.visible
+
+                sourceComponent: HMxcImage {
                     id: avatarToolTipImage
                     fillMode: Image.PreserveAspectCrop
                     animatedFillMode: AnimatedImage.PreserveAspectCrop
                     clientUserId: avatarImage.clientUserId
-                mxc: avatarImage.mxc
                     title: avatarImage.title
+                    mxc: avatar.toolTipMxc
+                    sourceOverride: avatar.toolTipSourceOverride
 
                     sourceSize.width: avatarToolTip.dimension
                     sourceSize.height: avatarToolTip.dimension
@@ -109,3 +113,4 @@ Rectangle {
             }
         }
     }
+}