feat: refactor notification controller initialisation

[Prithpal-Sooriya]

Explanation

Separates out the controller constructor and initialisation. This makes it easier to integrate with the Modular Initialisation approach in extension and mobile.

BREAKING it would now require the controller to explicitly call init after being constructed to be correctly setup. E.g.

const notificationServicesController = ...

// This needs to be done
notificationServicesController.init()

References

Changelog

@metamask/notification-services-controller

• REMOVED: BREAKING - refactored out the NotificationServicesController constructor initialisation methods. You must explicitly call the .init() method to initialise controller
• ADDED: init method to initialise NotificationServicesController

Checklist

• I've updated the test suite for new or updated code as appropriate
• I've updated documentation (JSDoc, Markdown, etc.) for new or updated code as appropriate
• I've highlighted breaking changes using the "BREAKING" category above as appropriate
• I've prepared draft pull requests for clients and consumer packages to resolve any breaking changes