Push cameraserver downstream from base_system.mk.

Some non-phone form factors don't want cameraserver to save storage and RAM.
Pushing it down to handheld and other build files allows selective inclusion to
happen there.

Intended to be a no-op refactoring, will disable for ATV in a follow-up CL.

Bug: 118369095
Test: built system image for random device as smoke test
Change-Id: I260fa5c9e512341d6a6824afebd5e8273fa5e66c
Merged-In: I260fa5c9e512341d6a6824afebd5e8273fa5e66c