feat: Node pools can enable fast_socket

[fraenkel]

fixes #2199

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[apeabody]

/gcbrun

[apeabody]

Thanks for the contribution @fraenkel!

[apeabody]

/gcbrun

[apeabody]

Thanks @fraenkel - The Terraform looks good to me, please also add the new field to the node pool documentation here: https://github.com/terraform-google-modules/terraform-google-kubernetes-engine/blob/master/autogen/main/README.md?plain=1#L186

[fraenkel]

The READMEs have been updated.

[apeabody]

/gcbrun

[apeabody]

validated fast_socket is present in v6.10