[FEATURE] Get-PnPSearchConfiguration support for Refinable managed properties

Describe the solution you'd like
Get-PnPSearchConfiguration currently returns all custom managed properties. Unfortunately, while this would have been sufficient for on-prem SharePoint, any time you need properties to be refinable or sortable in SPO, you have to map crawled properties to the existing refinable managed properties (e.g., RefinableString00, RefinableDate19). I would like for the Get-PnPSearchConfiguration to be able to retrieve any of these properties that have mappings.

Describe alternatives you've considered
There is no other alternative that I've found. There does not appear to be any way within Graph or SPO REST to retrieve managed properties.

Additional context
I'm attempting this as part of a broader attempt to use Microsoft 365 DSC, which utilizes PnP.PowerShell.

Start at the Get-PnPSearchConfiguration cmdlet and review the SharePoint search-schema guidance linked in the issue. Compare its current handling of custom managed properties with mapped RefinableString and RefinableDate properties. Done means the cmdlet can retrieve refinable or sortable properties that have mappings, supporting the Microsoft 365 DSC use case.