chaininterface+multi: add filter_block and reentered to ChainWatchInterface

chaininterface+multi: add filter_block and reentered to ChainWatchInterface

Because filter_block takes a  and returns a list of s , we must add a lifetime to the ChainWatchInterface, which bubbles up in a lot of places. These places include adding a lifetime  to the Node struct, which causes a lot of rearranging tests so that variables don't go out of scope before the Node that owns them does.