This PR makes progress on #7711 by identifying any common prefix of the
paths in the file finder's search results, and replacing the "interior"
of that prefix---every path segment but the first and last---with `...`,
when a heuristic indicates that the longest path would otherwise
overflow the modal.

The elision is not applied to any segment that contains a match for the
search query.

There may be more work to do on #7711 in the case of long result paths
that do not share a significant common prefix.

Release Notes:

- Improved display of long paths in the file finder modal

Co-authored-by: Max <max@zed.dev>