head: fix skipping other files when getting errors from reading

[lauchimoon]

Fixes #13127.

The issue was that head_file was returning early in case of an error, making uu_head exit early and ignore the rest of files to be processed.

The fix catches the error given by head_file, prints it, and keeps iterating over each file.

[github-actions]

GNU testsuite comparison:

Skipping an intermittent issue tests/cut/bounded-memory (passes in this run but fails in the 'main' branch)
Skipping an intermittent issue tests/misc/tty-eof (passes in this run but fails in the 'main' branch)
Skipping an intermittent issue tests/pr/bounded-memory (passes in this run but fails in the 'main' branch)
Note: The gnu test tests/tail/pipe-f is now being skipped but was previously passing.
Note: The gnu test tests/env/env-signal-handler was skipped on 'main' but is now failing.

[cakebaker]

Can you please add a test to tests/by_util/test_head.rs to ensure we don't regress in the future? Thanks.

[lauchimoon]

Hello @cakebaker, I added the test checking against /dev/video0. Let me know if it's good.

[codspeed-hq]

Unable to generate the performance report

There was an internal error while processing the run's data. We're working on fixing the issue. Feel free to contact us on Discord or at support@codspeed.io if the issue persists.