LibWeb: Support transforms, stroking, gradients, etc for SVG <text>

This makes use of the new Gfx::Path::text() to handle SVG text elements,
with this text is just a regular path, and can be manipulated like any
other graphics element.

This removes the SVGTextPaintable and makes both <text> and geometry
elements use a new (shared) SVGPathPaintable. This is identical to the
old SVGGeometryPaintable. This simplifies painting as once something is
resolved to a Gfx::Path, the painting logic is the same.

Tests/LibWeb/Ref/reference/svg-text-effects-ref.html

@@ -0,0 +1,15 @@
+<style>
+  * {
+    margin: 0;
+  }
+  body {
+    background-color: white;
+  }
+</style>
+<!-- To rebase:
+  1. Open svg-text-effects.html in Ladybird
+  2. Resize the window till there's x and y scrollbars
+  3. Right click > "Take Full Screenshot"
+  4. Update the image below:
+-->
+<img src="./images/svg-text-effects-ref.png">