src: modernize cleanup queue to use c++20

[anonrig]

Getting the idea from @jasnell on #56059, let's use std::ranges::sort and spaceship operator to sort with std::ranges::sort which is available on C++20.

[codecov]

Codecov Report

Attention: Patch coverage is 72.72727% with 3 lines in your changes missing coverage. Please review.

Project coverage is 87.98%. Comparing base (4cf6fab) to head (77309d7).

Files with missing lines	Patch %	Lines
src/cleanup_queue.h	71.42%	1 Missing and 1 partial ⚠️
src/cleanup_queue.cc	75.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #56063      +/-   ##
==========================================
- Coverage   88.00%   87.98%   -0.03%     
==========================================
  Files         656      656              
  Lines      188988   188991       +3     
  Branches    35992    35971      -21     
==========================================
- Hits       166315   166275      -40     
- Misses      15838    15891      +53     
+ Partials     6835     6825      -10     

Files with missing lines	Coverage Δ
src/cleanup_queue.cc	82.35% <75.00%> (-3.37%)	⬇️
src/cleanup_queue.h	86.66% <71.42%> (-13.34%)	⬇️

... and 37 files with indirect coverage changes