fuzzer web interface: add a UI element showing a list of source files sorted by total uncovered points of interest

[andrewrk]

Extracted from #20958.

• Scrollable box that lists all source files
• Along with file name, show coverage percent
• Sort the list descending by percent uncovered

Additionally there should be a quick filter box at the top to limit which files show up in the box based on the query.

Selecting a file from the list should navigate the source view to that file.

Related:

• fuzzer web interface: put the source view into a scrolling box so the main UI doesn't go offscreen #20984