Queued request controller to flush queue on network change for a domain

[BelfordZ]

          The selected network can change in other circumstances as well. For example if the user switches the network dropdown in the popup, according tot he designs it should also update the dapp-selected network (I know that's not implemented yet, but it will be soon).

So we may want to trigger this flushing somewhere else, which would capture both cases. e.g. when the state changes, or in a method responsible for making that state change

Originally posted by @Gudahtt in https://github.com/MetaMask/core/pull/4064#discussion_r1526651126