Re-enable PaintTouchActionRects

This patch re-enables PaintTouchActionRects after the following changes:
crrev.com/606921 - Ensure PaintChunk::hit_test_data is updated in a cached subsequence
crrev.com/607236 - Paint replaced hit test rects without background
crrev.com/607238 - Paint hit test rects when acceleration skips bg

These fixes address all known issues.

Bug: 903480
Change-Id: I8ae56a1b97b5d9345508a8193a55097a9040bd89
Reviewed-on: https://chromium-review.googlesource.com/c/1334330Reviewed-by: Xida Chen <xidachen@chromium.org>
Reviewed-by: Xianda Sun <sunxd@chromium.org>
Commit-Queue: Philip Rogers <pdr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#607991}

third_party/blink/renderer/platform/runtime_enabled_features.json5

@@ -904,7 +904,7 @@
     // Compute touch action rects in paint instead of ScrollingCoordinator.
     {
       name: "PaintTouchActionRects",
-      status: "test",
+      status: "stable",
     },
     // PaintTracking enables the Largest Text Paint metric, Last Text Paint
     // metric, Largest Image Paint metric and Last Image Paint metric.