Merge Extension AccountsTrackerController with the core one

[mcmire]

These controllers are similar but have separate implementations. We will need to dive into how they are used in the extension vs. mobile app to understand what a combined version should look like.

While we are doing this, we may need to:

• Extract any API interactions or complex utility functions
• Refactor to be more easily understood
• Write comprehensive unit tests

Additionally, there are patches in mobile around AccountTrackerController under @metamask/assets-controllers, and we will want to make sure those are integrated as well.

[desi]

Notes: Extension has support for single call balances contract to do a balance update with a single call and we need that feature on the one on core.