pyproject: Drop hatchling in favor of setuptools and also drop dunamai

hatchling's insistence on valid specifiers causes inevitable build failures on older distros as described in

https://github.com/pypa/hatch/issues/1368

Instead of fixing the root cause of this problem, upstream decided to add an env var to override it requiring custom patches in million places.

Use good old setuptools instead, whose maintainers actually care about distro packaging and users in general.