Parameterize ThroughputScorer

This makes the salient parameters of ThroughputScorer configurable
via an overlay.

Set the default parameters so that unmetered networks are preferred
over metered networks, and within each of those categories, saved networks
are preferred over suggestions. However, being the last-suggested network
can override both of these for a limited time.

Bug: 136675430
Bug: 142081306
Test: atest FrameworksWifiTests (currently 1 disabled)
Change-Id: I54ba20c93a99c3bd3e261faca1b0ec3f1c46e50a
5 files changed