[MBL-1609] Handle no add-ons/no reward cases in the add-ons VC

[ifosli]

📲 What

Handle the no rewards and no add-ons case for bonus support in the add-ons view controller.

Note: This also handles wiring up the bonus support to the pledge vc (in a super quick way and tags the tech debt ticket to actually remote the bonus support class/references from the pledge vc entirely).

👀 See

Jira

No reward case	No add-ons case

♿️ Accessibility

Untested since it's not adding any new UI components

✅ Acceptance criteria

• Add-ons VC is always presented in the newly organized flow
• Bonus support/pledge amount is settable and validated (continue button is disabled if it's too high)
• Pledge VC presents correct bonus support/pledge amount value to user

⏰ TODO

• New string should use translatable version instead of being hard-coded. I'll update that before submitting if the string translations are ready.