Count the external (receiving) keys available in the keypool.
Declared in <wallet/wallet.h>
[[requires_capability(0x7f2e1e598d68), requires_capability(0x7f2e11aa9b28), requires_capability(0x7f2e169ff918), requires_capability(0x7f2e15f2edb8), requires_capability(0x7f2e12c6da48)]]
size_t
KeypoolCountExternalKeys() const;
The number of external keys in the keypool.