gpg: Fix regression for the recent malicious subkey DoS fix.
* g10/packet.h (PUBKEY_USAGE_VERIFY): New. * g10/getkey.c (get_pubkey_for_sig): Pass new flag also to requested usage. (finish_lookup): Introduce a verify_mode.
- Fixes-commit: 48978ccb4e20866472ef18436a32744350a65158
- GnuPG-bug-id: T7547