Add benchmark for ls_cmd using a ext4 test image of around 1000 files

[yunzheng]

This PR adds a benchmark test for the ls_cmd in target-shell and a new test fixture providing an ext4 image with around 1000 files for doing the directory listing.

The benchmark is in preparation of implementing #1577 and some other related issues, which will contain some refactoring regarding efficiency.

The test image is derived from debian-live-13.3.0-amd64-standard.iso and only the /bin dir and some files from /etc are copied over. The file contents in /bin are also all sparse (NULL bytes) so the image compresses well. The test data mainly focuses on what is useful for directory listings, such as filenames, permissions, owner and group.

The compressed test image itself is only 100kb.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 81.09%. Comparing base (42285ac) to head (15acc76).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1622   +/-   ##
=======================================
  Coverage   81.09%   81.09%           
=======================================
  Files         402      402           
  Lines       35264    35264           
=======================================
  Hits        28599    28599           
  Misses       6665     6665           

Flag	Coverage Δ
unittests	81.09% <ø> (ø)

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[codspeed-hq]

Merging this PR will not alter performance

✅ 12 untouched benchmarks
🆕 4 new benchmarks

Performance Changes

	Benchmark	BASE	HEAD	Efficiency
🆕	test_benchmark_ls_bin[cold_cache-]	N/A	423.3 ms	N/A
🆕	test_benchmark_ls_bin[warm_cache--l]	N/A	4 s	N/A
🆕	test_benchmark_ls_bin[warm_cache-]	N/A	425.3 ms	N/A
🆕	test_benchmark_ls_bin[cold_cache--l]	N/A	4 s	N/A

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_{Comparing benchmark-ls-cmd (15acc76) with main (42285ac)}