Update aws-vpc-cni and cni-metrics-helper charts for v1.16.3 release

[jdn5126]

Issue

N/A

Description of changes

[aws-vpc-cni]

• updated VPC CNI image tags to v1.16.3
• updated Network Policy agent image tag to v1.0.8

[cni-metrics-helper]
ref: aws/amazon-vpc-cni-k8s#2748

• added variable for custom pod annotations

Checklist

• Added/modified documentation as required (such as the README.md for modified charts)
• Incremented the chart version in Chart.yaml for the modified chart(s)
• Manually tested. Describe what testing was done in the testing section below
• Make sure the title of the PR is a good description that can go into the release notes

Testing

Manually verified that chart could be rendered and applied to a cluster.

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