Add installation type to backup information file

Add information about the type of installation from which the backup tarball was made. This is needed because Helm chart based installations create a tarball that is different than that made by other installations (the former bundles files residing in object storage also).

Related to https://gitlab.com/charts/gitlab/issues/808.

• Changelog entry added, if necessary
• Documentation created/updated
• Tests added for this feature/bug
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides