Removing import clixml mocks from dbatools koans

[shaneis]

PR Summary

Removes the dependency on importing XML files for [PSCustomObject]s in the actual files.

Context

Adds mocks for each dbatools koan to the required file themselves.

Changes

Moved the Import-Clixml for [PSCustomObject] code in the files

Checklist

• Pull Request has a meaningful title.
• Summarised changes.
• Pull Request is ready to merge & is not WIP.
• Added tests / only testable interactively.
  • Make sure you add a new test if old tests do not effectively test the code changed.
• Added documentation / opened issue to track adding documentation at a later date.