Add resource settings for AADUser with docs

[FabienTschanz]

Pull Request (PR) description

This PR adds the new function Get-M365DSCResourceSettings to the M365DSCUtil module and includes documentation on how to skip the MemberOf processing for the AADUser resource.

In tenant cloning scenarios, especially when migrating users and / or groups, the members of the groups or the groups itself might not exist. This introduces issues, where errors might occur if a member is not found (because it doesn't exist) or assigning a user to a group fails (because it too doesn't exist). With using the resource setting AADUserApplyMemberOf with either true or false, it's possible to stop processing the MemberOf and only let the AADGroup manage the members. This solves the problem when creating users first and only after all of the users exist, then the groups are deployed. If this was not the case and a group wouldn't exist, errors would be thrown and the configuration would need to be applied multiple times until it succeeds.

This Pull Request (PR) fixes the following issues

None.

Task list

• Added an entry to the change log under the Unreleased section of the file CHANGELOG.md.
  Entry should say what was changed and how that affects users (if applicable), and
  reference the issue being resolved (if applicable).
• Resource parameter descriptions added/updated in the schema.mof.
• Resource documentation added/updated in README.md.
• Resource settings.json file contains all required permissions.
• Examples appropriately added/updated.
• Unit tests added/updated.
• New/changed code adheres to DSC Community Style Guidelines.