Clean up vfolder statuses

[fregataa]

This is a follow-up to #1892 and #713.

One entity should have only one state machine.
Let's leave VFolderOperationStatus only.

• Merge VFolderAccessStatus into VFolderOperationStatus
• Change or merge VFolderFilterStatusFailed, VFolderFilterStatusNotAvailable to VFolderOperationForbidden or VFolderNotFound and update error message for client
• Allow ensure_vfolder_status to get multiple statuses

Tasks

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1. fix: VFolder file listing not working #2072
   area:docs comp:manager size:L type:bug +4
   

[achimnol]

VFolderAccessStatus is an alias mapping to VFolderOperationStatus.
#2072 will rename it to make this clear, and ensure_vfolder_status() will be refactored to a decorator.

[achimnol]

Let's clarify the meaning or future implementation plan of VFolderOperationStatus.MOUNTED, or remove it.