[#562] cmd/neofs-ir: use NEP-6 wallet for keys

Also remove neofs-crypto uses from `pkg/innerring`.

Signed-off-by: Evgenii Stratonikov <evgeniy@nspcc.ru>

pkg/util/config/crypto.go

@@ -0,0 +1,34 @@
+package config
+
+import (
+	"errors"
+
+	"github.com/nspcc-dev/neo-go/pkg/encoding/address"
+	"github.com/nspcc-dev/neo-go/pkg/wallet"
+)
+
+// LoadAccount loads NEP-6 load, unlocks and returns provided account.
+func LoadAccount(path, addr, password string) (*wallet.Account, error) {
+	w, err := wallet.NewWalletFromFile(path)
+	if err != nil {
+		return nil, err
+	}
+
+	defer w.Close()
+
+	h, err := address.StringToUint160(addr)
+	if err != nil {
+		return nil, err
+	}
+
+	acc := w.GetAccount(h)
+	if acc == nil {
+		return nil, errors.New("account is missing")
+	}
+
+	if err := acc.Decrypt(password); err != nil {
+		return nil, err
+	}
+
+	return acc, nil
+}