cryptsetup: convert pkcs11/fido2 to iovec for key handling

cryptsetup: convert pkcs11/fido2 to iovec for key handling

key-data might be NULL. Fixes crash:

0  0x0000559c62120530 in attach_luks_or_plain_or_bitlk (cd=0x559c6b192830, name=0x7ffd57981dc4 "root", token_type=TOKEN_FIDO2, key_file=0x0, key_data=0x0, passwords=0x0, flags=524296, until=0)
    at ../src/cryptsetup/cryptsetup.c:2234
        pass_volume_key = false
        r = 1469577760
        __func__ = '\000' <repeats 29 times>
1  0x0000559c6212279c in run (argc=6, argv=0x7ffd5797fe98) at ../src/cryptsetup/cryptsetup.c:2597
        discovered_key_data = {iov_base = 0x0, iov_len = 0}
        key_data = 0x0
        token_type = TOKEN_FIDO2
        destroy_key_file = 0x0
        flags = 524296
        until = 0
        passphrase_type = PASSPHRASE_NONE
        volume = 0x7ffd57981dc4 "root"
        source = 0x7ffd57981dc9 "/dev/disk/by-uuid/8372fb39-9ba4-461a-a618-07dcaae66280"
        status = CRYPT_INACTIVE
        tries = 0
        key_file = 0x0
        config = 0x7ffd57981e05 "luks,discard,fido2-device=auto,x-initrd.attach"
        use_cached_passphrase = true
        try_discover_key = true
        discovered_key_fn = 0x7ffd5797fa70 "root.key"
        passwords = 0x0
        cd = 0x559c6b192830
        verb = 0x7ffd57981dbd "attach"
        r = 0
        __func__ = "\000\000\000"
2  0x0000559c621231e6 in main (argc=6, argv=0x7ffd5797fe98) at ../src/cryptsetup/cryptsetup.c:2674
        r = 32553
        __func__ = "\000\000\000\000"

Follow-up for 53b6c99018f918a5d2c9000ac5fe3a2440115ea7