Count the external (receiving) keys available in the keypool.
Declared in <wallet/wallet.h>
[[requires_capability(0x7f94fde05818), requires_capability(0x7f95061a8558), requires_capability(0x7f94f2b79068), requires_capability(0x7f94f0cf7cf8), requires_capability(0x7f94fee3a6e8)]]
size_t
KeypoolCountExternalKeys() const;
The number of external keys in the keypool.