WiFiMetrics: Count hidden & passpoint networks

1. Extended the WiFiMetrics proto to include counts for hidden and
passpoint networks, counting these for all saved networks, connections
and scan results.
2. Extended the counting of Open, Personal and Enterprise network to
include scans.
3. Extended ConnectionEvent logging to detect and flag passpoint network
connections.
4. Implemented the checks that detect if a scan Result is a hidden network.
While I was here: Cleaned up a couple old WifiMetrics <TODO>s, which we will not be doing.
BUG=28634987

Change-Id: I2e22bf8d79ccbda84ead700272ff0f1b0f13d2e7
Test: Extended unit tests, executed manually
7 files changed
tree: 91659b1317a2c676357dc9dce3919b0eaff1ab5b
  1. service/
  2. tests/