Unicorn/Sidekiq: some settings are not implemented or not configurable

Currently, unicorn and sidekiq pods ConfigMaps contain versions gitlab.yml.erb which do not implement some settings, and have some settings that are currently hard-coded (unconfigurable).

Missing:

• default_theme: part of the GA demo scorecard.
• issue_closing_pattern
• webhook_timeout
• [ ] repository_downloads_path: No benefit here in the charts unless you could set it to a volume for caching. (But doing so would require a ManyWrite volume in order to let unicorn write to it, and sidekiq clean it up, so out of scope for now)
• [ ] shared: Should not be needed with object storage support. Primarily affects only unicorn/workhorse
• [ ] webpack: Not needed
• [ ] workhorse: Not directly needed, allows configuration of secret path.
• incoming_email
• gravatar Defaults work with gravatar.com
• sidekiq(.log_format)
• pseudonymizer (needs pseudonymizer.yml implemented)
• extra for Google Analytics / Piwik

Unconfigurable

• default_project_features
• gitlab_ci
• kerberos.enabled: Should this be?
• gitlab_shell.(received,upload)_pack Should this be?