modify system messages handling for chat signaling

[mahibi]

there needs to be a special system messages handling regarding signaling

• handle and translate the important ones

• request server via insurance request for others instead to handle the message

ref https://github.com/nextcloud/spreed/blob/fd1807d0017d736b3d058a830f720defc670a6a0/lib/Signaling/Listener.php#L80-L101
ref https://github.com/nextcloud/spreed/blob/bf0f5f05e42b9d94449970c09836978650b1a514/lib/Chat/Parser/SystemMessage.php#L118

[anakin78z]

Partially implemented in #6124