Fix test that made no sense

[graebm]

Issue
While reviewing PR #1170 (comment) (which fixed an invalid index warning in this test), I gave this test a good hard look, and realized it was broken. As I slowly made sense of this test, I found another way it was broken.

Research:
This hash table test was added with the original hash table PR #17.

That branch had 2 different authors, which seems to have led to the brokenness

• Original commit with this test
• In this commit, author B accidentally replaces floating-point-rand with integer-rand, breaking randomness so this test doesn't actually test anything anymore
• In this commit, Author A removes some entries[i -1] checks that don't really make sense because entries isn't sorted
• In this commit, Author B brings the checks back. My guess is there was a merge conflict and they just accepted their own side

Description of changes

• Fix randomness
• Add comments about what this test is doing
• Fix the checks, using the sorted_entries array instead of the unsorted entries array

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 83.63%. Comparing base (da9e1c3) to head (1c1f929).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1172   +/-   ##
=======================================
  Coverage   83.63%   83.63%           
=======================================
  Files          57       57           
  Lines        5953     5953           
=======================================
  Hits         4979     4979           
  Misses        974      974           

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