feat: Integrate Snap notification services

[hmalik88]

Description

Write a short description of the changes included in this pull request, also include relevant motivation and context. Have in mind the following questions:

1. What is the reason for the change? Snap notifications were moved into the NotificationServicesController to reduce code duplication.
2. What is the improvement/solution? The NotificationController and associated code was deleted, as well as code that was written to process snap notifications. Parts of the codebase that expect snap notifications from the NotificationController source were also updated.

Pre-merge author checklist

• [ ] I've followed MetaMask Contributor Docs and MetaMask Extension Coding Standards.
• [ ] I've completed the PR template to the best of my ability
• [ ] I’ve included tests if applicable
• [ ] I’ve documented my code using JSDoc format if applicable
• [ ] I’ve applied the right labels on the PR (see labeling guidelines). Not required for external contributors.

Pre-merge reviewer checklist

• [ ] I've manually tested the PR (e.g. pull and build branch, run the app, test code being changed).
• [ ] I confirm that this PR addresses all acceptance criteria described in the ticket it closes and includes the necessary testing evidence such as recordings and or screenshots.