Get-SecureBootUEFI_DBXSVN should sort SVN's as [Version] type, instead of implicit string type

[garlin-cant-code]

Get-SecureBootUEFI_DBXSVN calls Get-SignatureDataSVN to return a string result, but this cannot be reliably sorted without prior conversion to [Version] type.

The latest BootMgr SVN is 8.0, but that could reach a two-digit major number in the next 12-24 months.