[WIP] Optimize the SaveLayer operation

[JsouLiang]

Description:

1. Create a PaintTree during the traversal tree phase, the PaintTree node is the AttributeLayer which set the paint attribute and it needs to saveLayer
2. In the DisplayListLayer we can get all the PaintTree nodes, and to compress the saveLayer op
3. In the AttributeLayer, we don't do the saveLayer op, instead, we create a PaintTree node and insert the node to the PaintTree.

• [x] Recording the attribute in a DlPaint
• [ ] Quick check which attribute is set in DlPaint
• [ ] Check if DlPaint is compatible with DLLayer's display_list

cc @flar

[flutter-dashboard[bot]]

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[JsouLiang]

Currently, we create a PaintNodeTree and every Layer Node will connect to a PaintNode. For the leaf node DLLayer, we can get a PaintNode branch which through parent can get all the saveLayer attributes, ex: for the DLLayer3 connect the ImageFilterPaintNode it can use Parent to get the Opacity and more. Cause for the leaf node or Container node can get all the saveLayer attributes, so we can optimize some SaveLayer op. cc @flar

[flutter-dashboard[bot]]

This pull request executed golden file tests, but it has not been updated in a while (20+ days). Test results from Gold expire after as many days, so this pull request will need to be updated with a fresh commit in order to get results from Gold.

[Hixie]

@JsouLiang is this PR still on your radar?