tests/tail: reduce delays in multiple tests to speed up execution

[domysu]

each changed test now completes in under 1 second each (down from 6–12 seconds)

each test was run 50 times sequentially on my machine to verify stability, no failures were observed.

Related to #10097

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/tail/inotify-dir-recreate (fails in this run but passes in the 'main' branch)
Skipping an intermittent issue tests/cut/bounded-memory (passes in this run but fails in the 'main' branch)
Skipping an intermittent issue tests/date/resolution (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.

[oech3]

Did this broke tail test on macOS?