Notebook scrolling perf improvement

[rebornix]

When scrolling a notebook, the notebook list view is creating cells, relayouting them and deleting them in a short period of time. Though we are using the same list view as the file explorer or settings editor, rendering a single notebook cell is much more costly. One typical improvement we can do is postponing rendering of costly component but it might harm the perceived experience (e.g. more flickering).

This PR tries to improvement the smoothness of scrolling by:

• Batch DOM write and read
  • When rendering the viewport, the list view will try to render all possible visible cells, insert their DOM nodes into the DOM tree
  • It will then check each one's dynamic height
  • In this PR, we will only check offsetHeight/clientHeight of output elements after all cells are initially rendered, to ensure that the layout is invalidated only once
• FastDomNode to avoid redundant DOM style updates
• transfom: translateY for updating top properties for focus indicator.