Add a large number of string comparison tests
Add a large number of string comparison tests

* Test comparing empty strings with cmp & leg

= Add a function to test various cases:
* Test same string but different in length
 ** Test reversed term returns opposite result
* Same string of various lengths but last grapheme is different
* Same length string but different character is in various locations
 ** Same as previous test, but the different character is a lower codepoint
    than previous test

bitrauser/roast,bitrauser/roast,dogbert17/roast,dogbert17/roast,perl6/roast