Display server response time with "zed query"

[philrz]

At the time this issue is being opened, Zed it at commit 266228f.

@mccanne recently expressed the following requirement:

I guess what I really want is for zui and zed query to print out how long the query took to execute (on the server). For zed query, could be an option. For zui, might want to always show it in the footer.

The Zui side is tracked in https://github.com/brimdata/zui/issues/2930, and this issue is to track the zed query side. I suspect that there may need to be API enhancements to provide this information in a place Zui can leverage it, so perhaps the two issues could be taken up simultaneously since zed as a client may leverage the same changes.