refactor: clean up the logs and reduce noise

- Remove "Detected Autocrypt-mime message" logs printed for every incoming Autocrypt message.
- Print only a single line at the beginning of receive_imf with both the Message-ID and seen flag.
- Print Securejoin step only once, inside handle_securejoin_handshake or observe_securejoin_on_other_device.
- Do not log "Not creating ad-hoc group" every time ad-hoc group is not created, log when it is created instead.
- Log ID of the chat where Autocrypt-Gossip for all members is received.
- Do not print "Secure-join requested." for {vg,vc}-request, we already log the step.
- Remove ">>>>>>>>>>>>>>>>>>>>>>>>>" noise from securejoin logs.

src/mimeparser.rs

@@ -278,7 +278,7 @@ impl MimeMessage {
 
         let public_keyring = keyring_from_peerstate(decryption_info.peerstate.as_ref());
         let (mail, mut signatures, encrypted) = match tokio::task::block_in_place(|| {
-            try_decrypt(context, &mail, &private_keyring, &public_keyring)
+            try_decrypt(&mail, &private_keyring, &public_keyring)
         }) {
             Ok(Some((raw, signatures))) => {
                 mail_raw = raw;