tr: use POSIX_FADV_SEQUENTIAL

[wtcpython]

Fixes #13121.

tr reads standard input sequentially but did not provide the kernel with a corresponding access-pattern hint.

Call fadvise with POSIX_FADV_SEQUENTIAL on standard input on supported platforms, treating it as a best-effort optimization so failures do not change command behavior. Add a Linux strace regression test that verifies the advice is issued.

[oech3]

It is useful for file input. Not for stdin (which is stream at most cases).

[oech3]

The test does not check that fadvise is properly called for file's fd.

[oech3]

OK. My issue is invalid at here:( . I misunderstood that pr accepts files as input.

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/cut/bounded-memory (fails in this run but passes in the 'main' branch)
Congrats! The gnu test tests/tail/pid is no longer failing!
Note: The gnu test tests/rm/many-dir-entries-vs-OOM is now being skipped but was previously passing.

[codspeed-hq]

Merging this PR will not alter performance

✅ 339 untouched benchmarks
⏩ 46 skipped benchmarks¹

---

_{Comparing wtcpython:tr-sequential-fadvise (8b8d5bf) with main (64bea9b)²}

Footnotes

1. 46 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. ↩

2. No successful run was found on main (738afee) during the generation of this report, so 64bea9b was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

[sylvestre]

@oech3 is that ok with you ?
thanks

[oech3]

This is useful for the case pr < file args which is probaly very nich usecase.