Add support for multiple redis instances segregated by persistence class (https://gitlab.com/gitlab-org/gitlab-ce/issues/30392)

Add support for multiple redis instances segregated by persistence class (https://gitlab.com/gitlab-org/gitlab-ce/issues/30392)

This issue exists to synchronize omnibus with changes to gitlab-ce.

Relevant documentation and discussion are in: https://gitlab.com/gitlab-org/gitlab-ce/issues/30392 and https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/11573