Feature: #97390 - Use password policy for backend user password in ext:install 

Description 

The password used to create the backend user during install (GUI and setup command) now considers the configurable password policy introduced in #97388.

Impact 

The globally configured password policy is now taken into account when the backend user is created during the install process.

For each violation of the password policy a message will be displayed to the user (GUI and setup command).