Show maximize/minimize icon for panes and terminal panel (#2521)

Closes
https://linear.app/zed-industries/issue/Z-1790/show-zoomunzoom-icons-for-panes-and-terminal-panel

![CleanShot 2023-05-24 at 11 07
04@2x](https://github.com/zed-industries/zed/assets/482957/b27d002c-6443-440b-88d0-cfa06d902477)

Antonio Scandurra committed 3y ago

8f49552121e2ff1c9aef1616d60f0983061a2081

Parents: 9575ffc , e5fd953

Committed by GitHub <noreply@github.com> on 5/24/2023, 9:44:39 AM