When the user closes a tab, the tab switcher will now select the tab at
the same position. This feature is especially relevant for keyboard
users when you want to close multiple consecutive tabs with
`<Ctrl-Backspace>`.

Please see the discussion at
https://github.com/zed-industries/zed/discussions/22791 for full
motivation and the quick demo.

Release Notes:

- tab_switcher: Preserve selected position when tab is closed