LibWeb: Layout SVG <text> elements during layout (not while painting)

Previously, all SVG <text> elements were zero-sized boxes, that were
only actually positioned and sized during painting. This led to a number
of problems, the most visible of which being that text could not be
scaled based on the viewBox.

Which this patch, <text> elements get a correctly sized layout box,
that can be hit-tested and respects the SVG viewBox.

To share code with SVGGeometryElement's the PathData (from the prior
commit) has been split into a computed path and computed transforms.
The computed path is specific to geometry elements, but the computed
transforms are shared between all SVG graphics elements.

Tests/LibWeb/Layout/input/svg-text-with-viewbox.html

@@ -0,0 +1,20 @@
+<svg viewBox="0 0 240 80" xmlns="http://www.w3.org/2000/svg">
+  <style>
+    .small {
+      font: italic 13px sans-serif;
+    }
+    .heavy {
+      font: bold 30px sans-serif;
+    }
+
+    .Rrrrr {
+      font: italic 40px serif;
+      fill: red;
+    }
+  </style>
+
+  <text x="20" y="35" class="small">My</text>
+  <text x="40" y="35" class="heavy">cat</text>
+  <text x="55" y="55" class="small">is</text>
+  <text x="65" y="55" class="Rrrrr">Grumpy!</text>
+</svg>