ln: Using unit test macros for ln and creating test cases for exception handling

[ChrisDryden]

Going through the coverlay of ln to see where we are missing coverage and found a few edge cases that I was looking to cover with tests. It was interesting to see that one of the error messages was actually impossible to reach on unix, so I ended up adding a cfg to only run it for windows.

I also updated the using of the macros in the tests since half of the tests were using them and half of them weren't

[github-actions[bot]]

GNU testsuite comparison:

Skip an intermittent issue tests/tail/overlay-headers (fails in this run but passes in the 'main' branch)

[github-actions[bot]]

GNU testsuite comparison:

Skipping an intermittent issue tests/tail/overlay-headers (passes in this run but fails in the 'main' branch)

[github-actions[bot]]

GNU testsuite comparison:

Skipping an intermittent issue tests/tail/overlay-headers (passes in this run but fails in the 'main' branch)

[codspeed-hq[bot]]

CodSpeed Performance Report

Merging #9625 will not alter performance

_{Comparing ChrisDryden:ln_testing_and_cleanup (3df36e3) with main (64203e3)}

Summary

✅ 127 untouched
⏩ 6 skipped[^skipped]

[^skipped]: 6 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports.

[github-actions[bot]]

GNU testsuite comparison:

Skipping an intermittent issue tests/tail/overlay-headers (passes in this run but fails in the 'main' branch)