unexpand: remove Box dyn - perf +7.5%

[oech3]

No description provided.

[codspeed-hq]

Merging this PR will improve performance by 7.52%

⚡ 2 improved benchmarks
✅ 307 untouched benchmarks
⏩ 46 skipped benchmarks¹

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
⚡	Simulation	unexpand_many_lines[100000]	145.8 ms	135.7 ms	+7.51%
⚡	Simulation	unexpand_large_file[10]	305.6 ms	284.2 ms	+7.52%

---

_{Comparing oech3:unex-dyn (b4318a8) with main (05466bb)}

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. ↩

[github-actions]

GNU testsuite comparison:

Congrats! The gnu test tests/tail/retry is no longer failing!
Congrats! The gnu test tests/cut/cut-huge-range is now passing!

[xtqqczze]

Can we define the enum like in comm.rs?:

coreutils/src/uu/comm/src/comm.rs

Lines 58 to 61 in 05466bb

	enum Input {
	Stdin(StdinLock<'static>),
	FileIn(BufReader<File>),
	}

[xtqqczze]

Contributes to #11811

[cakebaker]

Kudos for the performance improvement, thanks!