fix: correctly infer read stats from second mate

[balajtimate]

Description

• Update get_library_stats.py so that the read statistics from the second mate would correctly get inferred
• Report median as int instead of float (this fixes the issue with the zarp-cli integration htsinfer pipeline, as the results json md5sums wouldn't match unless the median was int)

Fixes #151

Type of change

• [X] Bug fix (non-breaking change which fixes an issue)

Checklist

Please carefully read these items and tick them off if the statements are true or do not apply.

• [X] I have performed a self-review of my own code
• [X] My code follows the existing coding style, lints and generates no new warnings
• [X] I have added type annotations to all function/method signatures, and I have added type annotations for any local variables that are non-trivial, potentially ambiguous or might otherwise benefit from explicit typing.
• [X] I have commented my code in hard-to-understand areas
• [X] I have added ["Google-style docstrings"] to all new modules, classes, methods/functions or updated previously existing ones
• [X] I have added tests that prove my fix is effective or that my feature works
• [X] New and existing unit tests pass locally with my changes and I have not reduced the code coverage relative to the previous state
• [X] I have updated any sections of the app's documentation that are affected by the proposed changes

If for some reason you are unable to tick off all boxes, please leave a comment explaining the issue you are facing so that we can work on it together.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (62fbf72) 100.00% compared to head (fccce2b) 100.00%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## dev #152 +/- ## ========================================= Coverage 100.00% 100.00% ========================================= Files 13 13 Lines 1109 1109 ========================================= Hits 1109 1109 ```

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