Update profile information in User Menu

Fixes https://github.com/vector-im/riot-web/issues/14158 (we needed an HTTP avatar URL)
Fixes https://github.com/vector-im/riot-web/issues/14159
Fixes https://github.com/vector-im/riot-web/issues/14157
Also fixes an issue where it wasn't updating automatically when the user changed their profile info.

This is all achieved through a new OwnProfileStore which does the heavy lifting, as we have to keep at least 2 components updated.

res/css/structures/_UserMenuButton.scss

@@ -35,9 +35,6 @@ limitations under the License.
             // Create another flexbox of columns to handle large user IDs
             display: flex;
             flex-direction: column;
-
-            // fit the container
-            flex: 1;
             width: calc(100% - 40px); // 40px = 32px theme button + 8px margin to theme button
 
             * {