feat: emit events for settings changes

[DNR500]

Jira: LF-10342

This PR as the settingUpdate event - this event will fire whenever the settings in the Widget are changed

Testing

Note: for testing I have been cherry-picking the addition of the WidgetEventsControl from the https://github.com/lifinance/widget/pull/309. its in this one commit. Once that PR is merged those changes will be available here as well

To test using the WidgetEventsControl

• Open Playground, go to the Playground settings and turn on the Dev view option
• The Widget events control should be visible in the playground
• You can toggle on event listener for settingsUpdated
• settingsUpdated event name with its payloads will be printed in the console

Using the event

To add a listener

widgetEvents.on(WidgetEvent.SettingUpdated, (payload) => console.log(payload))

The payload for the event will look like this...

{
  "setting": "slippage",
  "newValue": "0.4",
  "oldValue": "0.3",
  "newSettings": { ... } // all the settings values after the change
  "oldSettings": { ... } // all the settings values before the change
}

The above is for the slippage setting but each of the settings will emit an event when changed. This should cover - appearance, gasPrice, language, routePriority, enabledAutoRefuel, slippage, disabledBridges, enabledBridges, _enabledBridges, disabledExchanges, enabledExchanges and _enabledExchanges

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