3/ Simplify WM parsing on Winscope

- Use flicker class type as object type
- Use name from flicker
- Use stableID from flicker
- Refactor element visibility
- Rename `childrenWindows` to children to avoid creating a new property

Bug: 185516271
Test: build winscope and open WM traces
Change-Id: I582c0fe4ac48f8a503d1dccfbce437d489a50ca7
9 files changed