SetDefaultPublicURI should be usable without having to install legacy-admininterface

When setting e.g. defaultPublicURI in a module descriptor

  <properties>
    <property>
      <name>defaultPublicURI</name>
      <value>redirect:/demo-project.html</value>
    </property>
  </properties>

the related install task info.magnolia.module.admininterface.setup.SetDefaultPublicURI resides in magnolia-module-legacy-admininterface and is deprecated.

We should move this task to core or create a replacement for it.