This new API allows requesting multiple pieces of information about a
particular action in one go and also simplifies the burden for
GActionGroup implementations -- they need not implement all the separate
APIs now.
Found by GIR compiler when building gobject-introspection:
gir/gio-2.0.c:33525: Warning: Gio: g_tls_password_set_description: unknown
parameter 'flags' in documentation comment, should be one of 'password',
'description'
gir/gio-2.0.c:14568: Warning: Gio: g_action_group_action_state_changed: unknown
parameter 'state' in documentation comment, should be one of 'action_group',
'action_name', 'value'
Makes explicit the fact that you are interacting with the individual
action rather than the group and removes potential namespace conflicts
with classes implementing the interface (like g_application_activate()
vs g_application_activate_action()).
