tests: replace run() with succeeds() or fails()

[cakebaker]

This PR replaces a lot of run() calls in the tests with either succeeds() or fails() for better readability. It also fixes some small things I noticed while doing those replacements, for example, replacing .no_stdout().no_stderr() with .no_output().

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/timeout/timeout (fails in this run but passes in the 'main' branch)
Skipping an intermittent issue tests/misc/usage_vs_getopt (passes in this run but fails in the 'main' branch)

[sylvestre]

can we deprecate run() ? :)
(or make it private)

[cakebaker]

No, we still use it in tests, for example in test_chown.rs. There we suppress some failures if the tests are run in the CI.