Improve Helm Chart

[lucacome]

### Tasks
- [ ] #1967
- [ ] https://github.com/nginxinc/nginx-gateway-fabric/issues/2043
- [ ] Use chart-testing to install the Helm Chart
- [ ] https://github.com/nginxinc/nginx-gateway-fabric/issues/2044
- [ ] https://github.com/nginxinc/nginx-gateway-fabric/issues/2083
- [ ] Test Helm upgrade
- [ ] https://github.com/nginxinc/nginx-gateway-fabric/issues/2156

[github-actions]

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