[CS] Add a generic transport-specific information API

Add a generic transport-specific information container interface and
access methods. These can be used by a network factory to pass transport
(bearer)-specific network parameters to the app.

Bug: 117605977
Test: atest frameworks/base/tests/net/java/android/net (+new unit tests)
Change-Id: Ib7c83b677e1c02a2212265719813e648b0c9cc1b