fix: Prefer to encrypt if E2eeEnabled even if peers have EncryptPreference::NoPreference

First of all, chatmail servers normally forbid to send unencrypted mail, so if we know the peer's
key, we should encrypt to it. Chatmail setups have `E2eeEnabled=1` by default and this isn't
possible to change in UIs, so this change fixes the chatmail case. Additionally, for chatmail, if a
peer has `EncryptPreference::Reset`, let's handle it as `EncryptPreference::NoPreference` for the
reason above. Still, if `E2eeEnabled` is 0 for a chatmail setup somehow, e.g. the user set it via
environment, let's assume that the user knows what they do and ignore `IsChatmail` flag.

NB:
- If we don't know the peer's key, we should try to send an unencrypted message as before for a
  chatmail setup.
- This change doesn't remove the "majority rule", but now the majority with
  `EncryptPreference::NoPreference` can't disable encryption if the local preference is `Mutual`. To
  disable encryption, some peer should have a missing peerstate or, for the non-chatmail case, the
  majority should have `EncryptPreference::Reset`.

src/mimefactory.rs

@@ -652,7 +652,9 @@ impl MimeFactory {
 
         let peerstates = self.peerstates_for_recipients(context).await?;
         let is_encrypted = !self.should_force_plaintext()
-            && encrypt_helper.should_encrypt(context, e2ee_guaranteed, &peerstates)?;
+            && encrypt_helper
+                .should_encrypt(context, e2ee_guaranteed, &peerstates)
+                .await?;
         let is_securejoin_message = if let Loaded::Message { msg, .. } = &self.loaded {
             msg.param.get_cmd() == SystemMessage::SecurejoinMessage
         } else {