Add the ability to transfer the previous local Media folder to Azure Blob Storage

[canadacubachina]

Describe the bug

after enabling OrchardCore_Media_Azure, the previous image under App_data cannot be transfered to storage.

Orchard Core version

2.1.4

To Reproduce

same as #17590

Expected behavior

sync storage and media under App_Data

Logs and screenshots

[Piedone]

This isn't a bug, but a feature request. Just as switching the DB engine, or the hosting provider is an undertaking that you have to do manually, moving between storage providers requires you to copy the files.

Since deciding on the storage implementation (like anything related to hosting) is something you have do upfront, and maybe, maybe you change it a single time after a while, I'd consider this a really low priority thing.