Add pyinfra equivalent of geerlingguy.nfs

[wowi42]

The geerlingguy.nfs Ansible role is among the top 11 most-downloaded roles on Ansible Galaxy (~9M downloads). This issue tracks adding a pyinfra equivalent as an example in this repo.

This slot replaces a duplicate DataDog.datadog entry that appears twice in the Galaxy top 10 (same role under differing namespace capitalisations).

• Ansible Galaxy: https://galaxy.ansible.com/ui/standalone/roles/geerlingguy/nfs/
• Source: https://github.com/geerlingguy/ansible-role-nfs

Scope

• Port the role's core tasks to a pyinfra deploy / operations
• Cover the same Linux platforms where reasonable
• Expose equivalent configurable variables (exports, etc.)
• Document usage in a README

cc @wowi42