Prefer references to fully downloaded messages over partially downloaded messages

[link2xt]

Since #5458 messages may be assigned to a chat if they reference partially downloaded message. However if message contains multiple references and one of them is a reference to fully downloaded message, we should prefer this one.

For example, consider receiving these messages:

1. Fully downloaded message creating a group.
2. Partially downloaded message to this group, assigned to 1:1 chat.
3. Fully downloaded message to the group.
4. Partially downloaded message to the group, referencing (2) and (3). Currently it will be assigned to 1:1 chat, but we can assign it to a group.

This is a follow-up enhancement that can be done once #5644 is merged.