feat: add "e2ee encrypted" info message to all e2ee chats (#7008)

this PR adds a info message "messages are end-to-end-encrypted" also for
chats created by eg. vcards. by the removal of lock icons, this is a
good place to hint for that in addition; this is also what eg. whatsapp
and others are doing

the wording itself is tweaked at
https://github.com/deltachat/deltachat-android/pull/3817 (and there is
also the rough idea to make the message a little more outstanding, by
some more dedicated colors)

~~did not test in practise, if this leads to double "e2ee info messages"
on secure join, tests look good, however.~~ EDIT: did lots of practise
tests meanwhile :)

most of the changes in this PR are about test ...

ftr, in another PR, after 2.0 reeases, there could probably quite some
code cleanup wrt set-protection, protection-disabled etc.

---------

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

deltachat-rpc-client/tests/test_multidevice.py

@@ -36,6 +36,9 @@ def test_one_account_send_bcc_setting(acfactory, log, direct_imap):
     assert ac1.get_config("bcc_self") == "1"
 
     # Second client receives only second message, but not the first.
+    ev_msg = ac1_clone.wait_for_event(EventType.MSGS_CHANGED)
+    assert ac1_clone.get_message_by_id(ev_msg.msg_id).get_snapshot().text == "Messages are end-to-end encrypted."
+
     ev_msg = ac1_clone.wait_for_event(EventType.MSGS_CHANGED)
     assert ac1_clone.get_message_by_id(ev_msg.msg_id).get_snapshot().text == msg_out.get_snapshot().text