date: parse <digits>j as a local time of day

[eyupcanakman]

date -d 9j was rejected even though GNU reads it as 09:00 today. The military timezone J means local time, so a number followed by j/J (9j, 1230J) is just the bare time-of-day form. The fix strips the suffix and handles it like the bare number.

Fixes #12684.

[codspeed-hq]

Merging this PR will not alter performance

✅ 323 untouched benchmarks
⏩ 46 skipped benchmarks¹

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_{Comparing eyupcanakman:fix/date-military-j-time (832a239) with main (048f56e)}

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. ↩

[cakebaker]

I would perform the checks only once, on lines 433 - 435. It allows you to simplify the code above to something like:

Suggested change

	let time_digits = match input.strip_suffix(['j', 'J']) {
	Some(prefix)
	if !prefix.is_empty() && prefix.chars().all(|c| c.is_ascii_digit()) =>
	{
	prefix
	}
	_ => input,
	};
	let time_digits = input.strip_suffix(['j', 'J']).unwrap_or(input);

[eyupcanakman]

Done. Collapsed it to the single strip_suffix and dropped the redundant digit guard, since is_pure_digits already revalidates time_digits below.

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/date/resolution (fails in this run but passes in the 'main' branch)
Skipping an intermittent issue tests/timeout/timeout-group (passes in this run but fails in the 'main' branch)
Note: The gnu test tests/seq/seq-epipe is now being skipped but was previously passing.
Congrats! The gnu test tests/cut/bounded-memory is now passing!
Skip an intermittent issue tests/tail/tail-n0f (was skipped on 'main', now failing)