refactor repo architecture (dragoon/komodo!161)

## changelog
- `src/main.rs` has been moved to a new crate: `bins/saclin` which stands for **S**emi-**A**VID **CLI** in **N**ushell
- dependencies of `komodo` have been fixed
- Nushell and Rust tests have been split in the Makefile: by default, only Rust tests will run locally and Nushell tests and examples can be run manually if desired. The CI will still run everything.
- the README has been updated
- test images have been moved to `assets/`
- the majority of the old `./nu-utils/` module have been moved to internals of `./benchmarks/` and imports have been fixed
- `cargo.nu` has been moved to `./bins/` and a new `./bins/README.md` mentions it
- `./bins/saclin/` has been created and should be a self-contained Rust crate + Nushell module