Add approval widget support for zero approvals.

What does this MR do?

1. Adds support for zero approvals in the MR widget
2. Turns approval settings to always on on in the project settings

Screenshots (if relevant)

Before	After	Comment
N/A		Zero required approvals, unapproved with ability to approve
N/A		Zero required approvals, unapproved with no ability to approve
N/A		Zero required approvals, approved
tba		Two required, unapproved with approval rights
tba		Two required, unapproved with no approval rights
tba		Two required, one approved, with approval rights
tba		Two required, all approved

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests added for this feature/bug
• Conform by the code review guidelines
  • Has been reviewed by a UX Designer
  • Has been reviewed by a Frontend maintainer
  • Has been reviewed by a Backend maintainer
  • Has been reviewed by a Database specialist
• EE specific content should be in the top level /ee folder
• Conform by the merge request performance guides
• Conform by the style guides
• If you have multiple commits, please combine them into a few logically organized commits by squashing them
• Internationalization required/considered
• If paid feature, have we considered GitLab.com plan and how it works for groups and is there a design for promoting it to users who aren't on the correct plan
• End-to-end tests pass (package-qa manual pipeline job)

What are the relevant issue numbers?

#2452 (closed)