Prioritize Passpoint home network over roaming network in wifi picker

Displayed RSSI and SSID to connect to for a Passpoint credential
network will correspond to the strongest home network by RSSI, or if
no home networks are available, then the strongest roaming network.

Tracking bug for adding robolectric tests: b/122849296

Bug: 118705403
Test: manual
Change-Id: I72b8a8be636c442b7833e1b56f5ad2423f5c3e76