add new directory for rofs

[haywoodsh]

Proposed changes

Add emptyDir for the path /var/lib/nginx/state to the helm chart and manifest when using read-only file system. closes #7510 #7322

Validation

1. Deploy NIC with read only file system enabled. Wait until usage report is sent

   2025/03/24 13:20:58 [info] 26#26: usage report was sent
   

2. navigate to the file system of the NIC pod, the required directory /var/lib/nginx/state/ is present and the file nginx-mgmt-state has been created by NGINX without any errors.

   $ ls /var/lib/nginx/state/
   nginx-mgmt-state
   

Checklist

Before creating a PR, run through this checklist and mark each as complete.

• I have read the CONTRIBUTING doc
• I have added tests that prove my fix is effective or that my feature works
• I have checked that all unit tests pass after adding my changes
• I have updated necessary documentation
• I have rebased my branch onto main
• I will ensure my PR is targeting the main branch and pulling from my branch from my own fork