[feat]: Migrate individual packages from CIFS

[chrisguida]

This would enable fast bitcoin syncs (Start9Labs/bitcoind-startos#58), easy migrations from other platforms (LND and vaultwarden, for instance), etc. Could also be reversed to allow easy exporting of app data.

I'm picturing a "Migrate from CIFS" OS feature that works similarly to CIFS backup restore but doesn't do any decryption. Instead it just imports data from a particular CIFS network folder, replacing anything in that package's data volume with the contents of the CIFS folder.

As @ProofOfKeags mentioned in the bitcoind issue referenced above, this does seem like something that could be implemented using the actions API; however, I don't believe there's any current way for a package to access CIFS, without some significant changes to the OS. After more thought I've been wondering whether this wouldn't make more sense as a general OS feature rather than individually implementing in each package that needs it.

[dr-bonez]

I think it may actually be preferred to add support for cifs mounts to the Actions API. Then you could create an action for migrating data from external sources.