Configure Dev/Prod Cell to specify prefix for _gitlab_session

Overview

In Ability to prefix session cookies (gitlab-org/charts/gitlab!3773 - merged) we added a new field in helm chart global.rails.sessionStore.sessionCookieTokenPrefix which will generate the _gitlab_session cookie used for authentication with a specific:

_gitlab_session=cell2-5cf865011acc4f85f7d4842bfbb94ecf  # `cell2` is the prefix for this cookie

We will use this prefix to be able to route a request via the HTTP router. We need to configure the existing cells to specify the sessionCookieTokenPrefix