Add ENABLE_NFTABLES to VPC CNI

[jdn5126]

What type of PR is this?
feature

Which issue does this PR fix:
#2103
#1847

What does this PR do / Why do we need it:
This PR add a new environment variable, ENABLE_NFTABLES, that allows customers to switch from using iptables-legacy (default) to iptables-nft in aws-node pod.

It also updates cmd/aws-vpc-cni-init/main.go to use procsyswrapper and removes utils/sysctl. #2146 merged before I realized that procsyswrapper existed.

Output:

$ kubectl logs aws-node-xlqj9 -n kube-system -c aws-node
time="2022-12-08T00:37:34Z" level=info msg="Updating iptables mode to nft"
Installed /host/opt/cni/bin/aws-cni
Installed /host/opt/cni/bin/egress-v4-cni
time="2022-12-08T00:37:34Z" level=info msg="Starting IPAM daemon... "
time="2022-12-08T00:37:34Z" level=info msg="Checking for IPAM connectivity... "
time="2022-12-08T00:37:35Z" level=info msg="Copying config file... "
time="2022-12-08T00:37:35Z" level=info msg="Successfully copied CNI plugin binary and config file."

Exec Output:

$ kubectl exec aws-node-xlqj9 -n kube-system -c aws-node -- iptables -V
iptables v1.8.4 (nf_tables)

$ kubectl exec aws-node-vttvf -n kube-system -c aws-node -- iptables -V
iptables v1.8.4 (legacy)

If an issue # is not available please add repro steps and logs from IPAMD/CNI showing the issue:
N/A

Testing done on this change:
Manually verified that integration tests pass (IPv4 and IPv6).

Automation added to e2e:
None

Will this PR introduce any new dependencies?:
No

Will this break upgrades or downgrades. Has updating a running cluster been tested?:
This will not break upgrades or downgrades. A running cluster has been tested.

Does this change require updates to the CNI daemonset config files to work?:
Yes, this adds an environment variable to the CNI daemonset config.

Does this PR introduce any user-facing change?:
Yes

Add `ENABLE_NFTABLES` environment variable to VPC CNI to allow customers to use `iptables-nft` instead of default `iptables-legacy`

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.