Fix BLE scanning fallback for devices without extended advertising

[juhapellotsalo]

Check isLeExtendedAdvertisingSupported before disabling legacy mode, allowing devices to fall back to legacy scanning when extended advertising is not supported.

[andreevdenis]

scanSettings.setLegacy(false) - won't disable legacy advertisments .

setLegacy
Set whether only legacy advertisments should be returned in scan results. Legacy advertisements include advertisements as specified by the Bluetooth core specification 4.2 and below. This is true by default for compatibility with older apps.
Params:
legacy – true if only legacy advertisements will be returned

setLegacy(false) - enables extended advertisments (+legacy)

In my opinion in some cases bluetoothManager.adapter.isLeExtendedAdvertisingSupported returns true but phone actually can't receive extended for some reason. Need to figure out more reliable way to detect if extended supported or not.

[andreevdenis]

My try here. We ignore 3 first seconds of legacy data (for Air). If no extended received - we start working with legacy.
48e41a2