Add YANG 1.1 actions to cover inventory-related RPCs

There is a large number of RPCs (and notifications, to be dealt with separately) which take advantage of yang-ext:context-{instance,reference} around opendaylight-inventory.

All of these are Routed RPCs, an OpenDaylight extension, which have an equivalent in YANG 1.1 actions.

Add proper action definitions to cover these, so that the functionality is available through both RPCs and actions and deprecate the RPCs.

As actions have a different invocation strategy and are available only through RFC8040 northbound, this will provide an explicit migration step leading to removal of Routed RPCs.