Use png_data for favicon of bookmarks imported from HTML

[darkdh]

• 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).

fix #4339

requires brave/muon#64

Auditors: @bridiver, @bbondy

Test Plan:

1. Import bookmarks from HTML file
2. There should be favicon shows when show favicon option is on

[bbondy]

++