Upgrade @metamask/multichain-account-service to version 2.0.0

A new major version of `@metamask/multichain-account-service`, 2.0.0, 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.

Start by checking the project's dependency manifests for @metamask/multichain-account-service and confirm whether this project uses it. Upgrade the package to 2.0.0, then run the relevant project checks to identify compatibility issues; done means the project uses the requested version and its checks pass.

Written by the indexing model from the issue text.