slightly nicer and shorter QR and invite codes (#7390)

- sort garbage to the beginning, readable text to the end
- instead of `%20`, make use of `+` to encode spaces
- shorter invite links and smaller QR codes by truncation of the names

the truncation of the name uses chars() which does not respect grapheme clusters, so
that last character may be wrong. not sure if there is a nice and easy
alternative, but maybe it's good engoug - the real, full name will come
over the wire (exiting truncate() truncates on word boundaries, which is
maybe too soft here - names may be long, depending on the language, and
not contain any space)

moreover, this resolves the "name too long" issue from
https://github.com/chatmail/core/issues/7015

---------

Co-authored-by: Hocuri <hocuri@gmx.de>

deltachat-rpc-client/tests/test_securejoin.py

@@ -122,7 +122,7 @@ def test_qr_securejoin_broadcast(acfactory, all_devices_online):
         bob2.start_io()
 
     logging.info("===================== Alice creates a broadcast =====================")
-    alice_chat = alice.create_broadcast("Broadcast channel for everyone!")
+    alice_chat = alice.create_broadcast("Broadcast channel!")
     snapshot = alice_chat.get_basic_snapshot()
     assert not snapshot.is_unpromoted  # Broadcast channels are never unpromoted
 
@@ -135,8 +135,8 @@ def test_qr_securejoin_broadcast(acfactory, all_devices_online):
     alice_chat.send_text("Hello everyone!")
 
     def get_broadcast(ac):
-        chat = ac.get_chatlist(query="Broadcast channel for everyone!")[0]
-        assert chat.get_basic_snapshot().name == "Broadcast channel for everyone!"
+        chat = ac.get_chatlist(query="Broadcast channel!")[0]
+        assert chat.get_basic_snapshot().name == "Broadcast channel!"
         return chat
 
     def wait_for_broadcast_messages(ac):
@@ -184,7 +184,7 @@ def test_qr_securejoin_broadcast(acfactory, all_devices_online):
 
         chat_snapshot = chat.get_full_snapshot()
         assert chat_snapshot.is_encrypted
-        assert chat_snapshot.name == "Broadcast channel for everyone!"
+        assert chat_snapshot.name == "Broadcast channel!"
         if inviter_side:
             assert chat_snapshot.chat_type == ChatType.OUT_BROADCAST
         else: