Currently, libobs contains two inhibitors: the portal-based one, and the
regular one based on each desktop environment's session manager. The portal
inhibitor takes precedence over the session manager one, when available.
Like the session manager inhibitor, the portal inhibitor performs all D-Bus
calls synchronously in the calling thread, which can lead to stalls. This is
not a good practice.
Make the portal inhibitor asynchronous, by using g_dbus_connection_call()
instead of g_dbus_connection_call_sync(). If an uninhibit call is made
before the previous inhibit call finishes, cancel the inhibit call instead.
Fixesobsproject/obs-studio#5314