Add proxy_url into Input Prometheus Scrape Metrics

[ntheanh201]

Is your feature request related to a problem? Please describe.

I cannot scrape metrics from Prometheus due to the need to route through a proxy. Adding proxy_url would solve this.

Describe the solution you'd like

I would like the option to specify a proxy_url in the Prometheus Scrape Metrics configuration of Fluent-bit, allowing metrics to be collected through a proxy server.

Describe alternatives you've considered

Additional context

This issue affects our ability to collect and monitor metrics in environments with strict network policies. Being able to configure a proxy directly in Fluent-bit would simplify our setup and improve reliability.

[patrick-stephens]

I thought all were supported via the generic proxy approach: https://docs.fluentbit.io/manual/administration/http-proxy