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>

python/src/deltachat/testplugin.py

@@ -20,6 +20,12 @@ import deltachat
 from . import Account, account_hookimpl, const, get_core_info
 from .events import FFIEventLogger, FFIEventTracker
 
+E2EE_INFO_MSGS = 1
+"""
+The number of info messages added to new e2ee chats.
+Currently this is "End-to-end encryption available".
+"""
+
 
 def pytest_addoption(parser):
     group = parser.getgroup("deltachat testplugin options")
@@ -606,7 +612,7 @@ class ACFactory:
         ev = ac2._evtracker.get_matching("DC_EVENT_MSGS_CHANGED")
         msg = ac2.get_message_by_id(ev.data2)
         assert msg is not None
-        assert msg.text == "Messages are guaranteed to be end-to-end encrypted from now on."
+        assert msg.text == "Messages are end-to-end encrypted."
         msg = ac2._evtracker.wait_next_incoming_message()
         assert msg is not None
         assert "Member Me " in msg.text and " added by " in msg.text