Implement basic VcnConfig and VcnGatewayConnectionConfig

This change adds some of the basic fields in VcnConfig and
VcnGatewayConnectionConfig, plus adds a persistability layer to ensure
all VcnConfig(s) are disk-stable.

Bug: 163602123
Bug: 163594033
Test: New tests added, passing
Change-Id: I2e632532809e7768b284be376f2b0a77f634fef5
diff --git a/Android.bp b/Android.bp
index 26e7165..4b3c22d 100644
--- a/Android.bp
+++ b/Android.bp
@@ -314,6 +314,7 @@
         ":framework-telecomm-sources",
         ":framework-telephony-common-sources",
         ":framework-telephony-sources",
+        ":framework-vcn-util-sources",
         ":framework-wifi-annotations",
         ":framework-wifi-non-updatable-sources",
         ":PacProcessor-aidl-sources",