test: Port 6 prysk CLI tests to pure Rust (#12048)
## Summary
- Ports `command-version`, `command-login`, `command-unlink`,
`bad-flag`, `conflicting-flags`, and `no-args` prysk tests to Rust
integration tests.
- Adds `command_test.rs` (7 tests) and `no_args_test.rs` (7 tests) with
insta snapshots for complex outputs.
- Deletes the 6 corresponding `.t` files.
The `no-args` composable_config subcases now use isolated temp
directories per test, fixing a subtle prysk issue where the
`basic_monorepo` fixture leaked packages into the `composable_config`
output due to overlaying fixtures in the same directory.
