Add DomainVerificationService skeleton

Just the basic SystemService so that future CLs can add methods. Starts
the service in SystemServer, but effectively does nothing.

Exempt-From-Owner-Approval: Already approved by owners on main branch

Bug: 163565712

Test: none, just a skeleton

Change-Id: I1388423894e1e96511ab0f7de8ac5a7c2eea6de0