Expose @hide APIs needed by ParceledListSlice

Expose @hide APIs referenced by ParceledListSlice/
BaseParceledListSlice as public APIs.

ParceledListSlice will not be made a stable API
in Android R. Thus, allow it to be copied into
modules that need it by ensuring it does not use
any @hide APIs.

Bug: 145317012
Test: compiles
Change-Id: Ife85b66005ba22b03c09bf9446661368dea31945