There should be a way to have multiple `KeetaNetAnchorHTTPServer`'s routes combined

[ezraripps]

If a anchor wants to host an fx estimate anchor, and an asset movement anchor, they should be able to combine the routes of both servers into one KeetaNetAnchorHTTPServer to host both on the same port.

This could be in a new class that extends KeetaNetAnchorHTTPServer, overrides initRoutes, and groups routes of the KeetaNetAnchorHTTPServer classes that were passed in.

Nothing about the hosted servers would change, logs etc would stay the same. It should also be able to set the url of children, or enforce url is set properly (to the same value) with all the children if they have set.