Public Preview of Mixed Reality Cloud Service

[XiangyuL-Microsoft]

This is the first check-in of Azure PowerShell module for Mixed Reality Azure Resource Management.
All code had been reviewed and checked-in private repo

Checklist

• I have read the Submitting Changes section of CONTRIBUTING.md
• The title of the PR is clear and informative
• The appropriate change log has been updated
• The PR does not introduce breaking changes
• If applicable, the changes made in the PR have proper test coverage
• For public API changes to cmdlets:
  • the changes have gone through a cmdlet design review (Microsoft internal partners only)
  • the cmdlet markdown files were generated using the platyPS module

[adxsdkps]

Can one of the admins verify this patch?

[cormacpayne]

@azuresdkci add to whitelist

[cormacpayne]

@XiangyuL-Microsoft a few minor comments, otherwise this looks great