plugin XEP-0384: run profileConnected workflow in background:

XEP-0384 connection workflow can be very long when connecting after a while (due to
OLDMEMO migration notably), which can lead to bad UX.

It is not necessary to `await` it as `encrypt` and `decrypt` already wait for the plugin
to be initialized correctly, so the workflow is now run in background.

sat/plugins/plugin_xep_0384.py

@@ -1622,7 +1622,7 @@ class OMEMO:
         else:
             self.__text_commands.registerTextCommands(self)
 
-    async def profileConnected(  # pylint: disable=invalid-name
+    def profileConnected(  # pylint: disable=invalid-name
         self,
         client: SatXMPPClient
     ) -> None:
@@ -1630,9 +1630,9 @@ class OMEMO:
         @param client: The client.
         """
 
-        await self.get_session_manager(
+        defer.ensureDeferred(self.get_session_manager(
             cast(str, client.profile)
-        )
+        ))
 
     async def cmd_omemo_reset(
         self,