Count the external (receiving) keys available in the keypool.
Declared in <wallet/wallet.h>
[[requires_capability(0x7fd7422a79e8), requires_capability(0x7fd745cde5e8), requires_capability(0x7fd73e2a0ac8), requires_capability(0x7fd73e44ff68), requires_capability(0x7fd739990008)]]
size_t
KeypoolCountExternalKeys() const;
The number of external keys in the keypool.