[B4B] Only expand bookmark editor tree view for selected node

Currently, nodes that were expanded in the bookmarks editor view remain
expanded when the dialog is opened again with a different node. We want
them to collapse instead and only expand the nodes up until the selected
node (if it's a folder) or its parent (if it's a bookmark).

This change is behind the feature flag
`SyncEnableBookmarksInTransportMode`.

Bug: 416214578
Change-Id: I123c0c50c3563cf8910839be68c2bae0509494e7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6551517
Commit-Queue: Amelie Schneider <amelies@google.com>
Reviewed-by: David Roger <droger@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1461281}