Add missing collapse/expand arrows for bookmark folders in Sidebar

Description

Add missing collapse/expand arrows for bookmark folders in Sidebar

Steps to Reproduce

1. install latest nightly
2. launch Brave
3. import https://github.com/brave/qa-resources/blob/master/brave_sorted_1000.html
4. click on the Bookmarks icon in the Sidebar
5. look at the nested folders

Actual result:

Nested folders are missing the collapse/expand arrows

Expected result:

Compare with the native Bookmarks view

Reproduces how often:

100%

Brave version (brave://version info)

Brave	1.38.23 Chromium: 99.0.4844.51 (Official Build) nightly (x86_64)
Revision	d537ec02474b5afe23684e7963d538896c63ac77-refs/branch-heads/4844@{#875}
OS	macOS Version 11.6.3 (Build 20G415)

cc @simonhong @rebron

[aguscruiz]

@simonhong can we just reuse the bookmark manager’s styles, icons and sizes for the sidebar view?

Let me know if you need more specifics, but basically so they both look the same.

[stephendonner]

Closing as stale. @stephendonner I believe we addressed this issue before releasing bookmarks sidebar panel.

Yup, looks good to me with

Brave	1.47.33 Chromium: 107.0.5304.91 (Official Build) nightly (x86_64)
Revision	3d5948960d62418160796d5831a4d2d7d6c90fa8-refs/branch-heads/5304@{#1097}
OS	macOS Version 11.7.1 (Build 20G918)

The “twisties” – expand/collapse arrows – are back: