manager: add LIBJAMI_FLAG_NO_AUTOLOAD

This patch introduces an option to initialize
the daemon without loading any accounts or
conversations. Additionally, it offers the
capability to load accounts and conversations
as needed. This feature could be particularly
beneficial for iOS notification extensions to
decrease CPU and memory usage.

jami-client-ios#345
Change-Id: Ib2ceef2a1f7d7cb7e7d4f94a18dd3bfdc3a8989f