Fix bookmark hanger dialog overflow

[luixxiul]

Close #8634

Auditors:

Test Plan:

1. Change UI scale on about:preferences#advanced
2. Minimize the window size
3. Click the star icon
4. Make sure the hanger dialog is not broken

Test Plan 2:

1. Open about:autofill
2. Click "Add Address"
3. Make sure the autofill dialog is not broken

• 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).

Test Plan:

[luixxiul]

Also this PR should fix the overflow of commonForm mockup on about:styles.

[NejcZdovc]

LGTM