Ability for routing tree editor to print only subtree matching alert

[hartfordfive]

In some cases, a complex alerting manager config with many routes and receivers can result in a graph that becomes almost impossible to read in the routing tree editor. It would be convenient if it had the ability to also print out the whole sub-tree (including the matched yaml config blocks) a given set of labels has matched. It would also be nice if amtool config routes test command could also print this information and not just the end state receivers that match the given labels.