Code Modernization: Replace manual comparison logic with the spaceship operator <=>

[Soean]

Since WordPress has bumped its minimum supported PHP version to 7.4, we should take advantage of modern PHP features to clean up legacy comparison logic. This ticket proposes replacing manual "less than / greater than" ternary or if/else blocks with the ​spaceship operator <=>.

The spaceship operator was introduced in PHP 7.0. It performs three-way comparisons and returns -1, 0, or 1 accordingly. In many parts of the WordPress Core, we still use verbose logic that can be simplified.

<?php
return ($a < $b) ? -1 : (($a > $b) ? 1 : 0);

<?php
return $a <=> $b;

Trac ticket: https://core.trac.wordpress.org/ticket/64497

[westonruter]

In 61474:

Code Modernization: Utilize spaceship operator <=> in sort comparison logic.

Some replaced instances also fix a bug where the comparison function should have returned 0 as opposed to 1 or -1 as used in ternaries. This results in a performance improvement.

Developed in ​https://github.com/WordPress/wordpress-develop/pull/10717

Props soean, mukesh27, westonruter.
Fixes #64497.