IpConnectivity metrics: add version number

This patch adds a version field to ipconnectivity.proto and populates it
to 2, which is the logical version number for NYC-MR2.

Test: IpConnectivity{EventBuilder,Metrics}Test pass
Bug: 32127906

(cherry picked from commit d680d4c856f54bea0c60dea74ba4204822391e49)

Change-Id: If8f167c0dc4c1abe0e235e2adfd131168a4ddc52
5 files changed