This commit updates the VCN code to use CarrierConfig to store the restriction policy configuration, and notify policy listners when the CarrierConfig gets updated. Bug: 239104955 Test: atest FrameworksVcnTests(new tests) Test: atest CtsVcnTestCases Test: manually verified by overriding carrier configs Change-Id: Iaeb1871b7d9f5c3d1b4e5ec24cfbf79eea58256f