Use q20::{cmp_{equal,not_equal,{less,greater}{,_equal}},in_range} around the code

There're no acceptance criteria for this ticket. It exists to collect changes that introduce uses of the q20 versions of https://en.cppreference.com/w/cpp/utility#Integer_comparison_functions via Task-number:

Acceptance Criteria:

• pick two Qt libraries that are most likely to exhibit problems with integer comparison
• port these two libraries to the new functions
• bonus: write a clang-tidy fit-it for it (if not, make a follow-up ticket)