Upgrade @metamask/account-tree-controller to version 9.0.0

A new major version of `@metamask/account-tree-controller`, 9.0.0, is now available. This issue has been assigned to you and your team because you code-own this package in the `core` repo. If this package is present in this project, please prioritize upgrading it soon to unblock new features and bugfixes.

Search the repository's package manifests and lockfiles for @metamask/account-tree-controller, then inspect the package's current usage and release notes for version 9.0.0. Update the dependency wherever it is declared, resolve any resulting compatibility changes, and run the relevant test suite and build to confirm the extension still works.

Written by the indexing model from the issue text.