gpg: Use ECC KEM interface for decryption.
* g10/call-agent.c (agent_pkdecrypt): Use --kem=PGP for PUBKEY_ALGO_ECDH. * g10/pubkey-enc.c (ecdh_sexp_build): New. (get_it): Use ecdh_sexp_build for PUBKEY_ALGO_ECDH. And don't use pk_ecdh_decrypt since it's done by agent.
- GnuPG-bug-id: T7649
- Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>