Panic in `FromBytes` functions

[tomtau]

Right now, it seems FromBytes functions assume the byte slices in arguments have correct lengths -- if not, they'll panic.
This assumption should ideally be documented or more explicitly handled (e.g. by returning a nil or an error instead of a panic).

An example panic:

panic: runtime error: index out of range [1] with length 1

goroutine 9 [running]:
encoding/binary.bigEndian.Uint16(...)
        /usr/local/go/src/encoding/binary/binary.go:101
github.com/taurusgroup/frost-ed25519/pkg/frost/party.FromBytes(...)