Add HTTPS Certificate to prombench.prometheus.io

[Vandit1604]

Fixes #724

This PR aims to add an HTTPS certificate for prombench.prometheus.io using Cert-Manager and Let's Encrypt. Testing the setup locally has proven challenging. Here’s a summary of the modifications and approaches tried so far:

• Updated the Nginx Service type to NodePort from LoadBalancer for easier local access.
• Changed the Prometheus Service type to ClusterIP with Ingress managing external access.
• Configured the Ingress resource to handle TLS with the prombench-prometheus-tls secret for HTTPS.
• Modified /etc/hosts to map prombench.prometheus.io to 127.0.0.1 but it worked when I mapped it to Node IP and add the Host in the header when testing to
• Successfully triggered and verified the ACME HTTP-01 challenge by adding the node IP to /etc/hosts, but the challenge does not get solved automatically with the manifest setup.

I’d appreciate any guidance on how to test this locally. The Issue was because of DNS since after mapping in /etc/hosts I was able to solve the challenge(Tested via curl)
If there's a better way to test this locally. Please let me know.
Thank you!