qa: add test cases for fscrypt feature in kernel CephFS client
As per the documentation fscrypt is a (kernel) "library which filesystems can hook into to support transparent encryption of files and directories". It basically allows users to transparently encrypt files and directories: a user can simply set the key in a directory and all files within that directory will be encrypted. Note that this means that only the file data will actually be encrypted; the only metadata the is encrypted is the filename, everything else (timestamps, file size, xatttributes, etc) are visible for other users as long as they have the permissions to access them.
So far, only local filesystems support it (ext4, f2fs and ubifs), but it looks like there's nothing preventing CephFS to support it.