Braces/brackets no longer around sets & arrays

[philrz]

This change in behavior has been confirmed to be coincidental with the changes in #1108 ("Brim ZJSON Update", cc: @jameskerr).

At Brim commit 4796f3d that was right before that PR, we were still using squiggly braces around sets and square brackets around arrays to clearly communicate their structure (i.e. so the user would less surprised at having to use the in operator to do searches against them as named fields), such as shown for tx_hosts / rx_hosts for Zeek files events in the first screenshot below.

But then with commit c3e0caa that's associated with #1108, the brackets are gone.

[philrz]

This was restored some time ago, I believe when the Zed type system was implemented in JS via #1603.

In any case, I can verify that it's present in current Brim commit 0dcf10c. Specifically, sets are rendered with the same |[ ]|as they appear in ZSON:

Likewise for arrays, these are rendered with [ ] as in ZSON.

Looking at it closely now, I happen to find the gray font of the brackets to be so light that it's a little difficult to see, but now that the detailed type info also appears when I hover with the mouse, there's multiple ways we're communicating it.