Figure out a plan to handle Sidekiq versioning issues for canary deployment

This is one of several issues that was raised in https://gitlab.com/gitlab-com/infrastructure/issues/1944#note_38240450 and is required to unblock https://gitlab.com/gitlab-org/gitlab-ce/issues/34877

From https://gitlab.com/gitlab-com/infrastructure/issues/1944

"One complication discussed in Slack is that Sidekiq jobs may need to be versioned in some way, since it's possible for the Rails process to schedule new jobs or change parameters for an existing worker that are not present in older versions."

A lot of good comments follow, but should be summarized here since the original issue covered a lot of terrain.