[network-controller] Prevent inconsistent state during switch

[Gudahtt]

When the NetworkController switches networks, the state changes 3 times: once to update providerConfig, once to update the network metadata (e.g. the network status), and once to update the selectedClientId. In between these changes, the NetworkController state will be inconsistent (providerConfig will not match the selectedClientId, and the network status will be stale). These state changes are all synchronous, they don't depend on any network requests (the lookup step comes later).

We should update the NetworkController to make a single state change, rather than three. This would prevent the state from being inconsistent.