Old internal operating system utility helpers that had been deprecated since Odoo 14 have been removed. This keeps the codebase cleaner and reduces maintenance of outdated compatibility code, with minimal expected impact for business users.

We deprecated all those in 14.0, so 16.0 seems like a good time to remove them.

`getppid` was not deprecated but it doesn't seem useful to keep around: windows support was added to getppid in Python 3.2.