Forward proxy support for NGINX Plus R34

[sjberman]

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With R34, NGINX Plus allows NGINX customers to send their license usage telemetry to F5 via an existing enterprise forward proxy in their environment.

NGF should support these fields so a user can configure NGINX Plus to forward usage reports via a forward proxy solution.

mgmt {
    proxy HOST:PORT;
    proxy_username USER;    #optional
    proxy_password PASS;    #optional
}

https://nginx.org/en/docs/ngx_mgmt_module.html

Acceptance

• allow users to configure forward proxy fields for usage reports when running NGINX Plus
• sensitive data should be stored in a Secret by the user

Dev Notes:

• NIC implementation: https://github.com/nginx/kubernetes-ingress/pull/7560