Geo: Handle repository and wiki sync separately in Geo::ProjectSyncWorker

What does this MR do?

See https://gitlab.com/gitlab-org/gitlab-ee/issues/9446. This is alternative implementation of https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/9338

The intention is to remove repository_sync_due? and wiki_sync_due? call from ProjectSyncWorker and add extra options to selectively sync repositories or/and wikis. This effectively takes a decision on what to sync out of Geo::ProjectSyncWorker class, making its function more straightforward.

This implementation adds one extra query Geo::ProjectRegistry.find_or_initialize_by(project_id: project_id) per project sync (from a cron job) but it will/should be cached by PG and is not expensive at all. In return, we get a number of benefits. We can selectively sync repo or/and wiki and we can easily implement https://gitlab.com/gitlab-org/gitlab-ee/issues/5348

What are the relevant issue numbers?

closes https://gitlab.com/gitlab-org/gitlab-ee/issues/9446 and https://gitlab.com/gitlab-org/gitlab-ee/issues/9444

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated via this MR
• Documentation reviewed by technical writer or follow-up review issue created
• 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.
• EE specific content should be in the top level /ee folder
• For a paid feature, have we considered GitLab.com plans, how it works for groups, and is there a design for promoting it to users who aren't on the correct plan?
• Security reports checked/validated by reviewer

Closes #9446 (closed)