Link to Troubleshooting doc when Zui shows a connectivity error

[philrz]

As described in #1497, we've had a few incidents of users coming to Slack with tricky problems losing connectivity to the local Zed service behind their app. In some cases we've been able to help them figure it out, and some problems have remained a mystery. As a result, we've got a section in the Troubleshooting doc that shares what we know and provides tips, but that still leaves the challenge of making the user aware that the doc exists. This PR attempts to plug that gap by pointing them toward the doc in two places in the app where such a connectivity error occurs.

Demo.mp4

Re-reading that section of the Troubleshooting doc in current times, I recognize conditions have changed slightly since it was first written. When first written, the concept of the app connecting to remote lakes was something we knew was supported by the architecture but 100% of our users were using the app exclusively within their local desktops. Therefore the article was written as if the only reasons these errors could surface would be things like a local Zed service crash, a local firewall or anti-virus tool causing problems, etc. Now that "remote lakes" are something more easily configured in the app and described in its own article (albeit framed as an "advanced" guide) it's easy to see how these connectivity errors could come up in very ordinary circumstances, e.g., during a routine/temporary network outage. That made me slightly nervous that the text as it was written might sent a remote lake user down a rabbit hole of advanced debug when in fact a simple ping would suffice. So what I've included is a small adjustment to the top of that Troubleshooting section to nod toward the article about remote lakes before diving into the local debug details. It's probably not too big of a concern because a user that set up a remote Zed service already has a decent handle on the pieces, and a user connecting to such a remote service is likely to funnel their problems first through the person who's managing the remote Zed service. 🤞

Closes #1497

[nwt]

Looks good to me but I'll leave approval to @jameskerr.