Aggregate code coverage of all fuzz targets per benchmark

[DonggeLiu]

Extended from #354: Each function-under-test typically consists of 10 fuzz targets. Currently, aggregate_coverage_diff.py represents their total code coverage by the fuzz target with the highest coverage, assuming it includes all lines covered by other targets. While this assumption holds in most cases, incorporating the coverage data from all fuzz targets will yield a more accurate representation.

[dberardi99]

Hi @DonggeLiu could I work on this issue?

[DonggeLiu]

Sure, but could you please check if it is already fixed first? Thanks

[DonggeLiu]

And could you please finish the other issue before moving on to this one?

[dberardi99]

Sure, but could you please check if it is already fixed first? Thanks

Of course, I'll let you know asap

[DonggeLiu]

Freeing this as discussed, feel free to request later : )