Add combine() and equals() for NetworkCapabilities admin UIDs.

NetworkCapabilities#mAdministratorUids should be checked for equality
when combining NetworkCapabilities. Administrator UIDs should also be
included in NetworkCapabilities equals() and hashCode().

Bug: 147903575
Test: FrameworksNetTests
Change-Id: I803bdec80e27ee80d3a39844c5fb7aed584ab07d