refactor: rename data_dir to instance_dir

CHANGELOG.md

docker/docker-compose.yml

src/cli/args.rs

src/config.rs

src/lib.rs

src/luamod.rs

src/pgproto.rs

src/pgproto/tls.rs

src/tarantool.rs

test/conftest.py

test/generate_snapshot.py

test/int/test_audit.py

test/int/test_basics.py

test/int/test_cli_connect.py

test/int/test_cli_ux.py

test/int/test_compatibility.py

test/int/test_config_file.py

test/int/test_expelling.py

test/int/test_joining.py

test/int/test_plugin.py