Add OEM_PAID capability to system api

Some system apps should be able to request OEM_PAID networks.  This
makes a lot of sense when Android is used as in-vehicle infotainment
systems.

Clean cherry-pick of ag/3782591

Bug: 68762530
Test: runtest -x frameworks/base/tests/net/ -c android.net.NetworkCapabilitiesTest
Change-Id: I306f060c5a386ff4b82cd99a03dc037ce60ded6a
Merged-In: Ic164c4a29cd449a31b2f1c12c8c345bcc5dc77fa
Merged-In: I6e9c4130db23a4f1c89ce7e9071ae519a2b0b7ec