Add an 11.4.0 database dump with default_admin installed

Problem/Motivation

In #3624072: Remove claro from database dumps we switched Claro for stark in the update test fixture database dumps. This is partly because default admin doesn't exist in 11.3.x, so it's not possible to add it to a dump without manually editing it.

We could add an 11.4.x database dump that does have default admin installed, and that would probably make it easier to test any upgrade paths involving default_admin specifically or theme config in general.

Steps to reproduce

Proposed resolution

Remaining tasks

User interface changes

Introduced terminology

API changes

Data model changes

Release notes snippet