Rustimport

- Fixed path normalization approach having led to problems on windows (thanks mhandb)

- Fixed missing path normalization sometimes leading to problems on windows devices (thanks mhandb)

- Added compatibility for pyo3 [function signatures](https://pyo3.rs/v0.18.3/function/signature) (thanks Walnut356)
- Updated default pyo3 version to 0.18.3

---
**PyO3 compatibility note**: Templating-dependent extensions experiencing problems with the new pyo3 version need to either [migrate their code](https://pyo3.rs/v0.18.3/migration.html) or fix their dependency using a manifest-comment like this in their rust source file:

diff
// rustimport: pyo3

+ //: [dependencies]
+ //: pyo3 = { version = "0.16.2", features = ["extension-module"] }

- fixed infinite loop on windows during workspace check (thanks Walnut356)

- Fixed backwards-incompatible type hint

- Fixed bug in cli `build` command (thanks for reporting davystrong)
- Added colored cli output when supported
- Adjusted to deprecation of `importlib.abc.Loader.load_module()` method in Python 3.10
- Added and improved tests