Shorten overflowing paths in file finder

[cole-miller]

Closes #7711

This PR changes the file finder to shorten the path portion of each match by replacing a segment with ..., if it would otherwise overflow horizontally. Details:

• The overflow calculation is based on a crude linear width estimate for ASCII text at the current em width. No elision is done for non-ASCII paths.
• A path component will not be elided if it contains a matching position for the file finder's search, or if it's the first or last component.
• Elision is only applied when it is successful in shortening the path enough to not overflow.

Release Notes:

• Improved the appearance of the file finder when long paths are shown by eliding path segments

[cole-miller]

Before:

Screen.Recording.2025-02-20.at.23.01.26.mov

After:

Screen.Recording.2025-02-20.at.22.59.40.mov