LibWeb: Apply scroll boxes offsets after painting commands recording

With this change, instead of applying scroll offsets during the
recording of the painting command list, we do the following:
1. Collect all boxes with scrollable overflow into a PaintContext,
   each with an id and the total amount of scrolling offset accumulated
   from ancestor scrollable boxes.
2. During the recording phase assign a corresponding scroll_frame_id to
   each command that paints content within a scrollable box.
3. Before executing the recorded commands, translate each command that
   has a scroll_frame_id by the accumulated scroll offset.

This approach has following advantages:
- Implementing nested scrollables becomes much simpler, as the
  recording phase only requires the correct assignment of the nearest
  scrollable's scroll_frame_id, while the accumulated offset from
  ancestors is applied subsequently.
- The recording of painting commands is not tied to a specific offset
  within scrollable boxes, which means in the future, it will be
  possible to update the scrolling offset and repaint without the need
  to re-record painting commands.

Tests/LibWeb/Ref/scrollable-box-with-nested-stacking-context.html

@@ -0,0 +1,46 @@
+<link rel="match" href="reference/scrollable-box-with-nested-stacking-context-ref.html" />
+<style>
+    #scrollable-box {
+        width: 300px;
+        height: 500px;
+        overflow: auto;
+        position: relative;
+        border: 2px solid black;
+    }
+
+    .content {
+        height: 1000px;
+        background-color: lightblue;
+    }
+
+    .abspos {
+        position: absolute;
+        bottom: 0px;
+        right: 0px;
+        width: 150px;
+        height: 50px;
+        background-color: coral;
+        z-index: 1000;
+        display: flex;
+    }
+
+    .box {
+        background-color: magenta;
+        width: 100px;
+        height: 100px;
+        position: relative;
+        top: 0px;
+        left: 0px;
+    }
+</style>
+<div id="scrollable-box">
+    <div class="content">
+        Lots of scrollable content here!
+        <div class="box">box</div>
+    </div>
+    <div class="abspos"><div class="box">box</div></div>
+</div>
+<script>
+    const scrollContainer = document.getElementById("scrollable-box");
+    scrollContainer.scrollTop = 500;
+</script>