types fix

[rrrooommmaaa]

allow constructing keys from packet list of AllowedKeyPackets (includes Signature, UserId etc.), the reverse of toPacketList()

[larabr]

Thanks! These constructors should actually take AnyPacket, since those that are not AllowedKeyPackets are accepted and simply ignored -- they do not cause runtime errors.
That said, a PrivateKey constructor errors if it encounters Public(Sub)Key packets, and similarly a PublicKey will reject Private(Sub)Key packets.

We could improve the types in that sense, if needed, e.g. using Exclude.

[larabr]

My bad, Exclude can only be used with union types and it does nothing in this case. I'd have expected some sort of warning from the compiler at least.

[larabr]

Thanks for the fix! I've included it in #1522 , since it required a related type update.