Upgrade Gitaly to 1.9.0

What does this MR do?

Upgrade Gitaly, and remove code that has been transferred to Gitaly

What are the relevant issue numbers?

gitaly!1000 (merged), and gitaly#1420 (closed)

Does this MR meet the acceptance criteria?

• [-] Changelog entry added, if necessary
• Tests added for this feature/bug
• [-] Tested in all supported browsers
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides
• Link to e2e tests MR added if this MR has Requires e2e tests label. See the Test Planning Process.
• Security reports checked/validated by reviewer