Rewrite the DevTools flame chart to snap to the selected tree branch

The DevTools flame chart currently supports W-A-S-D keys to zoom and pan. Some flame chart implementations, like Perfetto's CPU flame chart, do not support these gestures. Instead, clicking on a stack frame will "snap" the chart to that specific branch of the tree. From the selected node up, all stack frames are rendered as single-parent-single-child relationships, and then the selected nodes children are rendered as normal. To "zoom out" or navigate up the tree, you can select once of the currently selected node's ancestors.

_perfetto's CPU flame chart_

This would help some of the performance issues we have with the current CPU flame chart (e.g. https://github.com/flutter/devtools/issues/3876) and also simplify the code. This also would make the experience similar to other CPU flame chart tools users are used to using.