Use the new Gitaly CommitDiff RPC

Conversation: gitaly#222 (closed)

What does this MR do?

We updated CommitDiff RPC, specifically the way we send patches along with diffs, so this MR updates the way we consume the response messages.

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

gitaly#229 (closed)