Respect excludes for followed broken symlinks

[Sean-Kenneth-Doherty]

Summary

• keep the override matcher available for fd-created broken symlink entries
• skip followed broken symlinks when they match --exclude before applying fd's remaining filters
• add a regression for --follow --exclude broken_symlink

Fixes #746.

Tests

• cargo fmt --check
• cargo clippy --all-targets --all-features -- -Dwarnings
• cargo test --test tests
• cargo test --locked
• manual: fd --follow --exclude broken_link . <tmp> now prints only the non-excluded file