Create empty VCN libraries

This is a prepartion CL to move VCN to its own libraries and
eventually migrate it from the non-updatable platform to Tethering
module.

This CL creates a new VCN directory with an empty java_sdk_library
and an empty java_library. In followup CLs, VCN source code will
be migrated to this VCN folder. VCN framework code and system
server code will be built into the two libraries.

Bug: 369703242
Test: build and boot
Flag: EXEMPT create new empty libraries; no functional change
Change-Id: I0f2e02771ac81a3d3fd588a6199be888ae299e52