Render labels using Text.QtRendering on OSX

Fonts were looking a bit to thick on when using `Text.NativeRendering`, so using `Text.QtRendering` instead. After this the font weight looks identical to figma (as far as I can see).

In this commit I also changed all `Label`'s to `UM.Label`'s and removed default properties where I could.

CURA-9154

plugins/DigitalLibrary/resources/qml/SelectProjectPage.qml

@@ -104,13 +104,12 @@ Item
                 width: parent.width - 2 * UM.Theme.getSize("thick_margin").width
             }
 
-            Label
+            UM.Label
             {
                 id: noLibraryProjectsLabel
                 anchors.horizontalCenter: parent.horizontalCenter
                 text: searchBar.text === "" ? "It appears that you don't have any projects in the Library yet." : "No projects found that match the search query."
                 font: UM.Theme.getFont("medium")
-                color: UM.Theme.getColor("text")
             }
 
             Cura.TertiaryButton