cpp: Output more properties of a subkey
* lang/cpp/src/key.cpp (ostream operator<< for Subkey): Fix wrong output of isInvalid and isDisabled flags. Add output of key grip, card serial number and the flags isSecret, isQualified, isDeVs, and isCardKey.
This makes it easier to check those properties for different keys, e.g.
with the run-keylist test program.
- GnuPG-bug-id: T5965