Add imap table to keep track of message UIDs

`imap` table maps Message-IDs to UIDs on the server. `dc_receive_imf`
no longer gets the UID of the message as an argument and does not
insert the folder and UID of the message into the `msgs`
table. `server_folder` and `server_uid` columns in `msgs` table are
deprecated.

MoveMsg and DeleteMsgOnImap jobs are removed. Now messages are moved
and deleted only in the `fetch_move_delete` procedure that consults
the `target` column of the `imap` table to determine where the message
should go.

Where the message should go is determined after prefetching by the
`imap::target_folder()` procedure.  Messages are only downloaded once
they reach their target folder to avoid race conditions in multidevice
setting, such as:

1. One device trying to FETCH the message while the other tries to
MOVE it.

2. One device marking the message as \Seen in the Inbox while the
other has already copied unseen message to the Movebox and is going to
delete the \Seen message in the Inbox.

3. Device downloads the message from the Inbox while there are newer
messages in the Movebox placed there by the other device, thus
processing the messages out of order.

python/tests/test_account.py

@@ -878,9 +878,13 @@ class TestOnlineAccount:
         acfactory.wait_configure_and_start_io()
         chat = acfactory.get_accepted_chat(ac1, ac2)
         chat.send_text("message1")
+
+        # Message is moved to the movebox
+        ac2._evtracker.get_matching("DC_EVENT_IMAP_MESSAGE_MOVED")
+
+        # Message is downloaded
         ev = ac2._evtracker.get_matching("DC_EVENT_INCOMING_MSG")
         assert ev.data2 > const.DC_CHAT_ID_LAST_SPECIAL
-        ac2._evtracker.get_matching("DC_EVENT_IMAP_MESSAGE_MOVED")
 
     def test_move_works_on_self_sent(self, acfactory):
         ac1 = acfactory.get_online_configuring_account(move=True)
@@ -1167,6 +1171,9 @@ class TestOnlineAccount:
 
         assert len(msg.chat.get_messages()) == 1
 
+        ac1.direct_imap.select_config_folder("mvbox")
+        ac1.direct_imap.idle_start()
+
         lp.sec("ac2: mark incoming message as seen")
         ac2.mark_seen_messages([msg])
 
@@ -1176,6 +1183,9 @@ class TestOnlineAccount:
 
         assert len(chat.get_messages()) == 1
 
+        # Wait for the message to be marked as seen on IMAP.
+        assert ac1.direct_imap.idle_wait_for_seen()
+
         # MDN is received even though MDNs are already disabled
         assert msg_out.is_out_mdn_received()
 
@@ -2651,11 +2661,7 @@ class TestOnlineAccount:
         msg = ac1._evtracker.wait_next_incoming_message()
         assert msg.text == "hello"
 
-        # Wait until the message was moved (if at all) and we are IDLEing again:
-        if inbox_watch == "1":
-            ac1._evtracker.get_info_contains("INBOX: Idle entering wait-on-remote state")
-        else:
-            ac1._evtracker.get_info_contains("IMAP-fake-IDLE: no folder, waiting for interrupt")
+        # The message has been downloaded, which means it has reached its destination.
         ac1.direct_imap.select_folder(expected_destination)
         assert len(ac1.direct_imap.get_all_messages()) == 1
         if folder != expected_destination: