tee: move aborted to MultiWriter

[oech3]

to dedup some code of #11943

[github-actions]

GNU testsuite comparison:

Skipping an intermittent issue tests/tail/tail-n0f (passes in this run but fails in the 'main' branch)

[codspeed-hq]

Merging this PR will improve performance by 4.82%

⚡ 1 improved benchmark
✅ 310 untouched benchmarks
⏩ 46 skipped benchmarks¹

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
⚡	Simulation	df_deep_directory	368.3 µs	351.4 µs	+4.82%

---

_{Comparing oech3:tee-aborted (e0a2dc4) with main (5aade31)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 (dd72eca) during the generation of this report, so 5aade31 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

[xtqqczze]

what does this help deduplicate, exactly?

[oech3]

aborted is accessed from its code path. It is difficult to add make helper fn to dedup if it is not part of MultiWriter.

[xtqqczze]

perhaps this change should be part of that future refactoring?

[oech3]

I need this soon. Is there any disadvantage for separating PR.

[xtqqczze]

I need this soon. Is there any disadvantage for separating PR.

it was harder to review when the motivation was unclear, but ok

[cakebaker]

@oech3 it's also fine to add multiple commits to a single PR if they belong together. Anyway, thanks!

[oech3]

Thankyou! I deduped #11943 (just -10 lines...).

I use different PR to make rebase easier.