Improve project start/stop performance by not always restarting ddev-router

[rfay]

Describe the bug

ddev-router is currently stopped and started for every ddev start. At least one reason for this is that the required ports may change when a new project is started. We can save a couple of seconds on every start by not doing that if the router is already going.

We can at least work around that precalculating the total router ports, perhaps maintaining them as docker labels. Alternately, this could b e the time to introduce global status, but I don't think so.

[mglaman]

One thing I would like to mention: I dislike the fact that Lando does not kill its router/proxy when all projects are stopped. You get stuck with a forever running landoproxyhyperion5000gandalfedition_proxy_1 container, which is pretty annoying.

I like the idea of ddev-router not having to be restarted whenever I start a second or third project. But if I run ddev stop and no other projects are running, I'd like the router to shut down.

[rfay]

We don't have any plans to change the current behavior, where turning off the last project stops the router. OTOH, the new ddev-ssh-agent will persist, as otherwise people would have to re-enter their passphrase, so the intention is it will persist until turned off.