fix: Loading overlay bugfix and cleanup (#10105)

* fix: reordering DOM output, simplifying styles, Emotionalizing

* simplification

* converting RefreshChartOverlay to TS

* Loading -> TS, stripping unused size prop

* simplification...

* just letting "position" prop act as a class name. Simpler!

* consolidating styles, changing a className prop to a position prop.

* nixing (unused) classname prop

* replacing inline loading img with the proper Loading component

* BY THERE.

* position prop is optional!

superset-frontend/src/SqlLab/components/TableElement.jsx

@@ -207,7 +207,7 @@ class TableElement extends React.PureComponent {
         </div>
         <div className="pull-right">
           {table.isMetadataLoading || table.isExtraMetadataLoading ? (
-            <Loading size={50} position="normal" className="margin-zero" />
+            <Loading position="inline" />
           ) : (
             <Fade in={this.state.hovered}>{this.renderControls()}</Fade>
           )}