uudoc: resolve shared Fluent keys across utility crates

[sylvestre]

No description provided.

[sylvestre]

example of the issue:
https://uutils.github.io/coreutils/docs-fr/utils/cksum.html

[github-actions]

GNU testsuite comparison:

GNU test failed: tests/cp/parent-perm-race. tests/cp/parent-perm-race is passing on 'main'. Maybe you have to rebase?
Skip an intermittent issue tests/pr/bounded-memory (fails in this run but passes in the 'main' branch)
Congrats! The gnu test tests/seq/seq-epipe is no longer failing!

[cakebaker]

clippy is not happy :|

error: implementation of inherent method `to_string(&self) -> String` for type `tests::SharedBuf`
     --> src/bin/uudoc.rs:970:9
      |
  970 | /         fn to_string(&self) -> String {
  971 | |             String::from_utf8_lossy(&self.0.lock().unwrap()).into_owned()
  972 | |         }
      | |_________^
      |
      = help: implement trait `Display` for type `tests::SharedBuf` instead
      = help: for further information visit https://rust-lang.github.io/rust-clippy/rust-1.94.0/index.html#inherent_to_string