audio/elevenlabs-cli: New port: Command-line interface for the ElevenLabs platform

The keyring crate's "vendored" feature makes libdbus-sys build a bundled
copy of D-Bus; files/patch-Cargo.toml drops it so the system library is
used instead. OPENSSL_NO_VENDOR does the same for openssl-sys.

The CLI exposes the whole ElevenLabs API as subcommands, so the generated
shell completions are about 6MB. They are gated behind a default-off
COMPLETIONS option; the man page is always installed.