Move deduceRestrictedCapability to libs/net and rename it

NetworkCapabilities is included in framework-connectivity, so external
module cannot have dependencies on its hidden API. Move the method to
libs/net so that external modules can use it by including the library.

Bug: 178777253
Test: FrameworksNetTests
(cherry-picked from ag/13921626)
Merged-In: I77970b3a5e5e0e9d263639694b1f06519169bf64
Change-Id: I77970b3a5e5e0e9d263639694b1f06519169bf64