find: show the file type and special bits in -ls

[youdie006]

Part of #890.

-ls used its own permission formatter, which only knew directories and regular files and ignored setuid, setgid and sticky bits: symlinks showed ?rwxrwxrwx, /dev/null ?rw-rw-rw- and /tmp drwxrwxrwx. This uses uucore::fs::display_permissions, which -printf %M already uses, and adds an integration test with a 4755 file and a symlink.

Against GNU find 4.9.0 the permission column now matches for every entry in a tree with special modes, a symlink, a broken symlink, a fifo and a socket, and for /dev/null. The missing -> target for symlinks, the date and the block count are unchanged here. cargo fmt --check, cargo clippy --all-targets -- -D warnings and cargo test pass.

Written with AI assistance (Claude); I have reviewed the change.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.34%. Comparing base (331a5c2) to head (bc99f80).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #892      +/-   ##
==========================================
+ Coverage   92.27%   92.34%   +0.06%     
==========================================
  Files          35       35              
  Lines        7576     7527      -49     
  Branches      393      384       -9     
==========================================
- Hits         6991     6951      -40     
+ Misses        443      438       -5     
+ Partials      142      138       -4     

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[codspeed]

Merging this PR will not alter performance

✅ 20 untouched benchmarks

---

_{Comparing youdie006:ls-permission-column (bc99f80) with main (331a5c2)}

[github-actions]

Commit bc99f80 has test result changes:

bfs testsuite:

Test results comparison:
  Current:   TOTAL: 316 / PASSED: 273 / FAILED: 37 / SKIPPED: 6
  Reference: TOTAL: 317 / PASSED: 274 / FAILED: 37 / SKIPPED: 6

Changes from main branch:
  TOTAL: -1
  PASSED: -1
  FAILED: +0

No result in this run (1) - hung, crashed, or renamed:
  ? posix/flag_comma (was PASS)