Create a new target service-connectivity to split
ConnectivityService from services.core.
Add ConnectivityServiceInitializer for initializing
ConnectivityService and add systemReady() in
ConnectivityManager so that SystemServer can call systemReady()
through ConnectivityManager which won't change current behavior.
Bug: 158268939
Test: make target-java, make host-java
atest FrameworksNetIntegrationTests
atest FrameworksNetTests
make, device can boot,
atest CtsStrictJavaPackagesTestCases
wifi and mobile data work.
Change-Id: Ie732bfaf381404af0bb599ca2f421a96e7aa4257
e6f27dd738