printf: omit errno from write errors

[floze-the-genius]

Summary

• strip Rust's trailing errno annotation from format write errors using the existing uucore helper
• add a Linux regression that writes printf output to /dev/full and checks the exact diagnostic and exit status

Validation

• cargo test --locked -p uucore --features format
• cargo test --locked --features printf --no-default-features --test tests test_printf::
• Linux Rust 1.88: 131 printf tests passed, 1 ignored
• cargo clippy --locked --features printf --no-default-features --test tests -- -D warnings
• cargo fmt --all -- --check

Closes #13851