Sync folder structure not kept

[AlexeyBarabash]

Things done in PR:

1. Orphaned bookmarks are placed to Pending Bookmarks folder and moved into actual parent folder once it arrived;
2. Pending Bookmarks and Deleted Bookmarks folder is hidden by BraveBookmarkPermanentNode
3. Fixed sorting issue of bookmarks tree with a lot of mixed child items/folder;
4. Added unit tests.

Fixes brave/brave-browser#2133

Submitter Checklist:

• 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).
• Verified that these changes build without errors on
  • Windows
  • macOS
  • Linux
• Verified that these changes pass automated tests (npm test brave_unit_tests && npm test brave_browser_tests) on
  • Windows
  • macOS
  • Linux
• Ran git rebase master (if needed).
• Ran git rebase -i to squash commits (if needed).
• Tagged reviewers and labelled the pull request as needed.
• Request a security/privacy review as needed.
• Add appropriate QA labels (QA/Yes or QA/No) to include the closed issue in milestone

Test Plan:

Manual is described in brave/brave-browser#2133 .
Auto tests: npm run test -- brave_unit_tests --filter=BraveBookmarkChangeProcessorTest.ItemAheadOfFolder:BraveBookmarkChangeProcessorTest.ItemAheadOfFolderAgressive:BraveBookmarkChangeProcessorTest.ItemAheadOfFolderRequireStrictSorting

Reviewer Checklist:

• New files have MPL-2.0 license header.
• Request a security/privacy review as needed.
• Adequate test coverage exists to prevent regressions
• Verify test plan is specified in PR before merging to source

[AlexeyBarabash]

Pushed a commit with fixes for this review notices, 454d445 . Will squash this commit after approval.

[darkdh]

we need to remove the observer hack and manually call set_visible(false) for both our permanent nodes. See the comments

[AlexeyBarabash]

master: f177732
0.59.x: 0a17159

[kjozwiak]

@AlexeyBarabash uplift request to 0.58.x approved after deliberating with @srirambv. 👍 Please add/remove needed labels and ensure that the associated issue is moved to the correct milestone.

[AlexeyBarabash]

Thanks @kjozwiak @srirambv

0.58.x aea975a