WiFi Health Tool

[bplattenburg]

Add a new tool to check the health of the local WiFi network. This includes both a UI and a HealthMetricProvider implementation. We should be able to leverage Android's WiFiInfo and related code to get the data.

This tool gets the values for first whether WiFi is connected, and if it is the ssid, bssid (the specific access point, useful to see if a single AP is overloaded), and signalStrength (based on rssi) of the connected network.

The UI simply displays all these values.

The HealthMetricProvider always provides the same connected boolean, and if connected the ssid, bssid, and signalStrength as the UI.

Its 'healthy boolean is somewhat configurable:

• if the device is not connected to WiFi it is always unhealthy
• If the ssid does not match an optional configuration value of "expectedSSID", it is unhealthy (covers enterprise scenarios where the customer wants to validate the devices are on the correct WiFi with the other peers).
• If the signalStrength is below an optional configured minimum value.

Open questions - should we scale the rssi into a 0-1 scale to match how Apple does it so that these can more easily be compared across platforms? Sync with development of getditto/DittoSwiftTools#148

[bplattenburg]

We may not be able to scale signalStrength to match what Apple does, if we're not confident we can create a truly comparable metric, just use raw rssi instead