Add a Setting for Zed lake service listening address

[philrz]

Background is in #1105.

I adopted some naming conventions from the Zed CLI tooling.

$ zed serve -h
NAME
    zed serve - service requests to a Zed lake
...
    -l [addr]:port to listen on (default ":9867")

i.e., I'm referring to the optional listening address portion as "addr".

The following video shows the feature in action such that the zed serve is launched with -l localhost:9867 by default and just -l :9867 when the setting is changed. I've also confirmed via the separate Zui running on my Windows laptop on the same LAN that changing the setting determines whether I can remotely access the lake behind my Macbook's Zui or not.

Demo.mp4

As the video shows, right now the app needs to be exited and restarted for the change to have effect, since zed serve is launched at startup time. @jameskerr and I discussed an early draft of this change and how we could take an approach similar to what we did with the "watch" functionality in #3049 such that when this setting is changed we immediately stop the launched lake service and restart it with the new settings. However, @jameskerr recognized that some code will probably need to be moved around to make that possible/clean and that exceeds my current skills, so I'll leave it to him to push commits to enable that functionality, if possible.

Closes #1105