regression test for wrong assertion

[TingDaoK]

Issue #, if available:

• The range test used a 16KB part size, so the test against 0.5MiB to 2MiB range is not hitting the case where the range we asked for is less than the part size. Since we always just ask for the start range + the part size.
• In the case if the range we asked for is less than the part size, the response will stop at the end of object.
• There was a bug where I mistake the object-size vs the content-length and fatal assert on it. It was fixed by https://github.com/awslabs/aws-c-s3/pull/604/files#diff-436560b33218855638d58d1c14ecca658afd2c8ec65f2b525e21c6d829a7068aL1419, but we didn't realize it could happen in real life.

Description of changes:

• Adding the regression test to make sure we test the case and we are handling it correctly.

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 89.13%. Comparing base (3f81fc9) to head (bcb0d1d).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #605   +/-   ##
=======================================
  Coverage   89.13%   89.13%           
=======================================
  Files          23       23           
  Lines        7585     7585           
=======================================
  Hits         6761     6761           
  Misses        824      824           

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