Update menu.js to rebuild when handling (add/remove) bookmark folders

[bsclifton]

• Submitted a ticket for my issue if one did not already exist.
• Used Github auto-closing keywords in the commit message.
• Added/updated tests for this change (for new code or code which already has tests).
• Ran git rebase -i to squash commits (if needed).

Update menu.js to also rebuild when handling (add/remove) bookmark folders

Fixes #4227

Auditors: @bridiver

Test Plan:

1. Launch Brave and ensure bookmarks toolbar is showing
2. Right click toolbar, choose Add Folder
3. Specify the name "1234" and hit save
4. Ensure "Bookmarks" menu is updated after saving
5. Save a bookmark inside of this folder
6. Verify "Bookmarks" menu looks correct

[bridiver]

looks good, but is there a test for it?

[bsclifton]

@bridiver there are webdriver tests for bookmarking- but not for adding a bookmark folder. I did look into this and unfortunately, we have electron popping up a system popup menu (versus our custom context menu, which we could test).

I tried simulating key presses but was unable to get it working. When I mentioned trying the keypress approach, the twitter acct for WebDriverIO said it's not possible. We could add an IPC shortcut or other mechanism for adding a folder but even then, I don't think system menus are testable (I would love to be wrong on this one)

[bridiver]

I think we have some other tests where we trigger the action directly

[bridiver]

see the pinned tab test and a few others

[bsclifton]

@bridiver tests added! thanks for calling out the missing tests and giving an example to check out 😄

[bbondy]

++

[srirambv]

Steps outlined works but not the expected behavior. Issue #4538 raised for the same