Test Directory Credentials before reimaging or avd host creation

Right now, if the AD or Entra admin credentials aren't valid the re image process starts and then fails at a point where the cleanup leaves you with no server. If this happens you can't create an AVD host either (since you don't have valid admin creds). So, if this happens it can leave you with no hosts and no way to fix it until the issue with the admin creds is resolved. If a test of the credentials could be added to the start of the process so a failure just results in an error in logs and the AVD host still being intact that would leave things in a functioning stat and allow more time to troubleshoot and fix the issue with the admin creds. Also having a way to manual test, the creds from the Intergrations->Directory screen would be great as well. I've had an issue where the creds are changed, and we aren't informed. A re-image happens and fails leaving things in a broken state that is then time critical to fix.