Support prometheus scrape metrics input plugin

[benjaminhuo]

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

There're requirements to collect prometheus metrics using fluentbit

Describe the solution you'd like

We need to support the prometheus scrape metrics input plugin. https://docs.fluentbit.io/manual/pipeline/inputs/prometheus-scrape-metrics

Additional context

We need to add hostNetwork field to fluentbit CRD to enable the fluentbit daemonset to scrape host node metrics directly from within a Pod such as using the following config to scrape application metrics on KubeEdge edge node:

[INPUT]
    name prometheus_scrape
    host 127.0.0.1
    port 10350
    tag edge-app-metrics 
    metrics_path /metrics/cadvisor 
    scrape_interval 15s