Tests/LibWeb: Restructure Ref and Screenshot test dirs to match others

Now each test type has the same directories:
- input
- expected
- data

Also, tests can be in subdirectories within ./input.

Tests/LibWeb/Ref/input/separate-borders-inline-table.html

@@ -0,0 +1,18 @@
+<link rel="match" href="../expected/separate-borders-ref.html" />
+<style type="text/css">
+    td {
+        border: 5px solid blue;
+        padding: 20px;
+    }
+
+    table {
+        border: 5px solid black;
+        display: inline-block;
+        border-collapse: separate;
+    }
+</style>
+<table>
+    <tr>
+        <td>A</td>
+    </tr>
+</table>