expose KeyringControler.verifyPassword

Currently we are validating passwords by calling `await KeyringController.submitPassword(credentials.password)` which is a heavy operation and is dramatically slowing down the UI. I see that base KeyringController has a [verifyPassword method](https://github.com/MetaMask/KeyringController/blob/520dad38bad52429bf997373d98e90d138d8ba7f/index.js#L189) that is not exposed by this wrapper. We could expose this method so we can check passwords without running a full update.

Start at the TypeScript wrapper around KeyringController, where password checks currently call submitPassword, and compare it with the linked base KeyringController.verifyPassword method. Expose the lighter verification entry point and confirm that callers can use it without triggering the full update operation.

Written by the indexing model from the issue text.