Use static map for VPN profile type in VpnConnectivityMetrics

Refactors VpnConnectivityMetrics to use a static SparseIntArray
to create a one-to-one mapping between VpnProfile types and the
VpnProfileType enum used for metrics reporting.

Bug: 429288223
Test: atest VpnConnectivityMetricsTest
Flag: EXEMPT PURE_REFACTOR
Change-Id: I5417646df311dbae66244aa721b9fc8b36cafd87