Return inet addr for discoverable printers

... by extending the RecommendationInfo to store the inet addresses not
just the count. Thankfully the recommendation plugins already contained
all the printers, not only the count.

Also expose the print service state as system APIs as they will be used
by the default print service.

Bug: 35765644
Test: Ran AddPrinterActivity on network that had printers to discover
Change-Id: I929a177adb75f6848848ba30a472cf0343d2e67e