Refactor tree utils

Refactor tree utils for proper reuse from IME viewers:
- add common/trace/trace_tree_node (factored out from viewers)
- rename renaming viewers/common/tree_utils -> viewers/common/ui_tree_utils
- add common/utils/tree_utils: generic tree utils reused from "trace" and "ui"

Bug: 238088679
Test: npm run build:all && npm run test:all
Change-Id: Ib14dd3495dc7e91e3a0eef2fdc20efa27fe1ef2e
24 files changed