Reduce perceived clutter in viewer reports

[tautschnig]

(moved over from https://github.com/diffblue/cbmc/issues/7865, reported by @ylevhariamzn)

CBMC version: 5.87 Operating system: Rocky Linux Exact command line resulting in the issue: What behaviour did you expect: What happened instead:

I am looking at the html report for both coverage, and assertion, violations, as my souce base is relatively large (400 include files, and 120 c files), I would like a way to "not" see all the cluter of the functions that my proff has not used

e.g

0.00 (0/37) some_file.c 0.00 (0/2) another_file.c 0.00 (0/16) more_files.c <further similar lines reporting 0% coverage follow>