Update Hash type from string to bytes

[NicolasMahe]

Because of mesg-foundation/engine#1270, hashes are now in bytes instead of string over the gRPC API.
The lib needs to be updated to reflect it.

The hashes should still be display to the user as base58 but also parsed from base58.
So it would make sense to add helpers function directly in the lib.

The marketplace service is using base-x to convert buffer to and from base58.