test: Replace help text integration tests with insta snapshots (#11911)
## Summary
- Deletes `turbo-help.t` (540 lines of inline expected help text) and
trims `no-args.t` (~120 lines of duplicated help text)
- Adds 6 insta snapshot tests for CLI help output (`turbo -h`, `turbo
--help`, `turbo link -h`, `turbo unlink -h`, `turbo login -h`, `turbo
logout -h`)
- Help text changes can now be reviewed and accepted with `cargo insta
review` instead of manually updating prysk test files
## Testing
```sh
cargo test -p turborepo-lib --lib "_help"
```