Add AppRoleMove.ps1 sample for migrating Default Access to an explicit app role (#3651)

Adds a Microsoft Graph PowerShell SDK sample that migrates users and groups
assigned the implicit "Default Access" role on an enterprise application to an
explicit "User" app role, with dry-run and report-only modes.

Authored by Jeevan Desarda. Provides a Microsoft-owned home for the script so
customers are not directed to run a tenant-modifying script from a personal
GitHub repository (relates to ADO work item 588327).

Co-authored-by: Jeevan Desarda <15001780+jeevansd@users.noreply.github.com>
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Co-authored-by: Ramses Sanchez-Hernandez <63934382+ramsessanchez@users.noreply.github.com>

Author: 4 people