Tidy up users of TRANSPORT constants.

Some call sites using explicit TRANSPORT types want to know about the
raw underlying transport, and they don't want to know about VPNs
that are going over that transport.

For example, SettingsLib always wants to know about the actual
Wi-Fi network, so it uses NOT_VPN to avoid being confused by VPN
networks that are backed by a TRANSPORT_WIFI network.

GnssLocationProvider wants to know about any validated internet
access, regardless of the underlying transport.

Test: atest com.android.settingslib.wifi
Bug: 68499889
Change-Id: Ib5897946d856444d9ff3b54c4aeace6baa42f8bf