[network-controller] Allow switching active chain without waiting for lookup

[Gudahtt]

When setActiveChain is called, the function does not resolve until the network lookup has completed. In some cases we just want tomorrow know when the NetworkController state was updated, and waiting for lookup is not desired.

We should allow the caller to not wait on lookup when switching the active chain (maybe by splitting this into two methods, or adding an option to control whether we wait).