Bug 1065279 - [settings] refactor Hotspot panel with AMD pattern

If you decide to use white-box testing instead, what you should test is whether `_init` initializes `this._settings` and calls to `_bindEvents` and `_updatePasswordIfNeeded` correctly, whether `_updatePasswordIfNeeded` calls to `_generateHotspotPassword` when there is no password, and whether `_generateHotspotPassword` generate valid password.