Should IFileInfo's PhysicalPath always be null?

Except for the `PhysicalFileInfo` implementation from the `PhysicalFileProvider`, it seems like `IFileInfo`'s `PhysicalPath` should always be null, especially when the implementation type doesn't use a physical file system.

This seems to be the case for known implementations like your own `ManifestEmbeddedFileProvider`'s `ManifestFileInfo`; and the expectation for a custom implementation like a possible `ZipArchiveFileProvider`'s `ZipEntryFileInfo` based on your `ZipArchive` and `ZipEntry`.

If this is the case, it would be nice to document this understanding... I suspect it's too late to suggest exposing `PhysicalPath` _only_ on the `PhysicalFileInfo`.

https://docs.microsoft.com/en-us/dotnet/api/microsoft.extensions.fileproviders.ifileinfo.physicalpath?view=dotnet-plat-ext-6.0#microsoft-extensions-fileproviders-ifileinfo-physicalpath

Inizia dalla documentazione dell'API IFileInfo.PhysicalPath collegata nell'issue, quindi confronta il comportamento documentato con PhysicalFileInfo, ManifestFileInfo e il caso personalizzato di ZipEntryFileInfo menzionato. Conferma se i provider di file non fisici debbano restituire null e aggiorna il riferimento dell'API per indicare chiaramente questa aspettativa.

Scritto dal modello di indicizzazione a partire dal testo della issue.