cni: customized calico manifests for single-stack IPv6

This is a set of customized calico CNI manifests to support single-stack
IPv6 cluster. Note that VXLAN is used since IP-in-IP currently only
supports IPv4.

References:
- https://docs.tigera.io/calico/latest/networking/ipam/ipv6#ipv6
- https://docs.tigera.io/calico/latest/getting-started/kubernetes/self-managed-onprem/config-options#switching-from-ip-in-ip-to-vxlan
- https://docs.tigera.io/calico/latest/networking/configuring/vxlan-ipip

Author: tthvo