Handle lockdown VPN reset intent in ConnectivityService

Currently, LockdownVpnTracker handles lockdown VPN reset intent.
Which will grab VPN object as a lock, then calls into
ConnectivityService to grab mVpn lock when querying NetworkInfo.
However, the order of grabing locks differs from ConnectivityService
and will causes deadlock if ConnectivityService grabs locks in
the other order.

Thus, make ConnectivityService handles reset intent so the
order of grabing locks can be consistent.

Test: atest FrameworksNetTests
Bug: 147403549
Change-Id: Ia10a3ef6f1e20d092a17313935083a84860961aa