feat: all commit operations return a potential GroupInfo

[beltram]

---

PR Submission Checklist for internal contributors

• The PR Title

  • conforms to the style of semantic commits messages¹ supported in Wire's Github Workflow²
  • contains a reference JIRA issue number like SQPIT-764
  • answers the question: If merged, this PR will: ... ³

• The PR Description

  • is free of optional paragraphs and you have filled the relevant parts to the best of your ability

---

What's new in this PR?

Issues

As exporting a GroupInfo (currently PublicGroupState) requires commit to be merged, we have all commit methods return a hypothetical GroupInfo which only becomes valid once the commit is merged

---

References

1. https://sparkbox.com/foundry/semantic_commit_messages
2. https://github.com/wireapp/.github#usage
3. E.g. feat(conversation-list): Sort conversations by most emojis in the title #SQPIT-764.