Migrate VCN to separate non-updatable libraries

This patch migrates VCN framework code from framework-minus-apex
to framework-connectivity-b, and VCN service code to
service-connectivity-b-pre-jarjar. This patch is part of the work
to move VCN to the Tethering module.

Design doc: go/mainline-vcn-eng-design

Bug: 369703242
Test: FrameworksVcnTests, CtsVcnTestCases, CtsStrictJavaPackagesTestCases
Flag: EXEMPT code refactoring; no functional change
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:ab8f06b5f32318dfd883e4bdd09e0d2a2c85a62e)
Merged-In: I747556281db2efab7115761147842d241fe283de
Change-Id: I747556281db2efab7115761147842d241fe283de