maturin: Update to 1.3.0, build as Python (host-only) package

maturin: Update to 1.3.0, build as Python (host-only) package

Python packages that use maturin to build do not call the maturin
program directly; they use the maturin build backend[1]. This build
backend is a Python library provided with maturin that interfaces with
the maturin program.

This changes the maturin package to use the Python build process so that
the build backend is installed correctly.

This also renames the source package to python-maturin and moves it into
the lang/python directory.

[1]: https://www.maturin.rs/#source-distribution

Signed-off-by: Jeffery To <redacted>