New APIs for message processing loops

This patch adds new C APIs
dc_get_next_msgs() and dc_wait_next_msgs(),
and their JSON-RPC counterparts
get_next_msgs() and wait_next_msgs().

New configuration "last_msg_id"
tracks the last message ID processed by the bot.
get_next_msgs() returns message IDs above
the "last_msg_id".
wait_next_msgs() waits for new message notification
and calls get_next_msgs().
wait_next_msgs() can be used to build
a separate message processing loop
independent of the event loop.

Async Python API get_fresh_messages_in_arrival_order()
is deprecated in favor of get_next_messages().

Introduced Python APIs:
- Account.wait_next_incoming_message()
- Message.is_from_self()
- Message.is_from_device()

Introduced Rust APIs:
- Context.set_config_u32()
- Context.get_config_u32()

deltachat-rpc-client/examples/echobot_no_hooks.py

@@ -6,7 +6,7 @@ import asyncio
 import logging
 import sys
 
-from deltachat_rpc_client import DeltaChat, EventType, Rpc
+from deltachat_rpc_client import DeltaChat, EventType, Rpc, SpecialContactId
 
 
 async def main():
@@ -30,9 +30,9 @@ async def main():
             await deltachat.start_io()
 
         async def process_messages():
-            for message in await account.get_fresh_messages_in_arrival_order():
+            for message in await account.get_next_messages():
                 snapshot = await message.get_snapshot()
-                if not snapshot.is_bot and not snapshot.is_info:
+                if snapshot.from_id != SpecialContactId.SELF and not snapshot.is_bot and not snapshot.is_info:
                     await snapshot.chat.send_text(snapshot.text)
                 await snapshot.message.mark_seen()