Element Call: fix widget shown while its still loading (waitForIframeLoad=false) (#12292)

* show loading spinner also if waitForIframeLoad = false
Configure EC so it waits for the content loaded action
!WARNING This breaks compatibility with the full mesh branch.
I would like to discuss here if/when we can do that.

Signed-off-by: Timo K <toger5@hotmail.de>

* stop show loading screen on widget ready (instead of preparing)

Signed-off-by: Timo K <toger5@hotmail.de>

* wait until widget loading is over before comparing screenshots

Signed-off-by: Timo K <toger5@hotmail.de>

* fix waitForIFrame=true widgets

Signed-off-by: Timo K <toger5@hotmail.de>

* test

Signed-off-by: Timo K <toger5@hotmail.de>

* always start with loading true. + cleanup

Signed-off-by: Timo K <toger5@hotmail.de>

* simplify loading

Signed-off-by: Timo K <toger5@hotmail.de>

* update snapshots (start not in loading state for waitForIframe = true widgets)

Signed-off-by: Timo K <toger5@hotmail.de>

---------

Signed-off-by: Timo K <toger5@hotmail.de>

test/components/views/elements/__snapshots__/AppTile-test.tsx.snap

@@ -47,7 +47,7 @@ exports[`AppTile destroys non-persisted right panel widget on room change 1`] =
         id="1"
       >
         <div
-          class="mx_AppTileBody mx_AppTileBody--large mx_AppTileBody--loading"
+          class="mx_AppTileBody mx_AppTileBody--large"
         >
           <div
             class="mx_AppTileBody_fadeInSpinner"
@@ -412,7 +412,7 @@ exports[`AppTile preserves non-persisted widget on container move 1`] = `
             </span>
           </div>
           <div
-            class="mx_AppTileBody mx_AppTileBody--large mx_AppTileBody--loading"
+            class="mx_AppTileBody mx_AppTileBody--large"
           >
             <div
               class="mx_AppTileBody_fadeInSpinner"