Refactor Dialog with Aphrodite

[luixxiul]

Closes #8984

Per 2dd92a9, dialog.less can be safely removed (as styles under 'menu' has been just copied).

Test Plan:

1. Open 'Import Browser Data...' from Bookmarks on the main menu
2. Open devtool
3. Make sure 'dialog' is styled properly

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).
• Ran git rebase -i to squash commits (if needed).

Reviewer Checklist:

Tests

• Adequate test coverage exists to prevent regressions
• Tests should be independent and work correctly when run individually or as a suite ref
• New files have MPL2 license header

[cezaraugusto]

is it needed somewhere? we are removing style class and I can't see any test using it.

[luixxiul]

oops I just forgot to check that out. I'm going to remove it, thanks.

[luixxiul]

Fixed with 3ba6110

[cezaraugusto]

I can't get enough of less less :)

[cezaraugusto]

I would recommend removing .dialog class since we're not using as far I can see. Other than that LGTM.

[luixxiul]

My bad, that conversion breaks the bookmarkHanger (which I often forget that it is also a component with Dialog). Fortunately the change is not available on 0.15.300 series, so I'm fixing it before 0.16.100. thanks!