[Oil-177] Add Opt-Out confirmation dialog

[phogel]

Displays Opt-Out confirmation window in advanced settings view when user tries to opt-out a purpose

• adds require_optout_confirm configuration parameter
• new text labels:
  • label_cpc_purpose_optout_confirm_heading
  • label_cpc_purpose_optout_confirm_text
  • label_cpc_purpose_optout_confirm_proceed
  • label_cpc_purpose_optout_confirm_cancel
• E2E tests
• Unit test