LibWeb: Add Skia painting command executor

This change introduces Skia painter available under a flag. It's not
yet match capabilities of Gfx::Painter and is not ready to replace it.

Motivation:
- The current CPU painter is a performance bottleneck on most websites.
  Our own GPU painter implementation is very immature and has received
  relatively little attention.
- There is ongoing effort on building painter that supports affine
  transforms (AffineCommandExecutorCPU) but it is far from being on par
  with the default CPU painter. Skia will allow us to immediately get
  full transformation support for all painting commands.

GPU painting:
I experimented with Ganesh GPU-backend, however profiling revealed that
without sharing viewport texture between WebContent and Browser
processes, it won't bring much performance improvement compared to
CPU-backend. Therefore, I decided to keep this PR focused on
implementing most of painting commands and switch to GPU-backend in
future changes.

Text rendring:
Skia painter uses glyph bitmaps produced by LibGfx. Using Skia for text
rendering will require large refactoring of the font rendering
subsystem. Currently, it's impossible to construct SkFont right before
rendering because Gfx::VectorFont can't be serialized back into sequence
of bytes.

There is a problem with ugly include paths like:
`#include <core/SkBitmap.h>`.
I would prefer to have skia prefix in the path. There was an attempt to
fix that but PR was rejected https://github.com/microsoft/vcpkg/pull/32660

Regressions compared to Gfx::Painter:
- DrawText is not implemented
- PaintTextShadow is not implemented
- PaintRadialGradient and PaintLinearGradient do not support "transition
  hints" and repeat length
- PaintConicGradient is not implemented
- DrawTriangleWave is not implemented
- DrawLine does not account for line style property
- DrawScaledBitmap and DrawScaledImmutableBitmap do not account for
  scaling mode property

vcpkg.json

@@ -7,6 +7,7 @@
     },
     "icu",
     "libjpeg-turbo",
+    "skia",
     "sqlite3",
     "woff2"
   ],
@@ -23,6 +24,10 @@
       "name": "libjpeg-turbo",
       "version": "3.0.2"
     },
+    {
+      "name": "skia",
+      "version": "124#0"
+    },
     {
       "name": "sqlite3",
       "version": "3.45.3"