feat: nfsd support as module package

[TMaYaD]

Build nfsd support as module package. This allows to build an nfsd extension to be used with projects like openebs/dynamic-nfs-provisioner.

Talos can load it via machine-config:

machine:
    # Configures the kernel.
    kernel:
        # Kernel modules to load.
        modules:
            - name: nfsd # Module name.

[tyriis]

any chance to get this pushed?

[AngellusMortis]

With 1.8 having a lot of focus on improving volume management, this might be a great thing to try to get in.