Add support for prometheus scrape config

[yuvraj-singh-3]

Description

Add support for custom prometheus scrape_configs in sysdig-agent configmap. Ref: https://prometheus.io/docs/prometheus/latest/configuration/configuration/#configuration-file
Example:

prometheus.yaml: |
  scrape_configs:
  - job_name: 'k8s-pods'
    tls_config:
      insecure_skip_verify: true
    kubernetes_sd_configs:
    - role: pod
    relabel_configs:
    - action: keep
      source_labels: [__meta_kubernetes_pod_host_ip]
      regex: __HOSTIPS__
    - action: keep
      source_labels: [__meta_kubernetes_pod_annotation_prometheus_io_scrape]
      regex: true
    metric_relabel_configs:
    - source_labels: [__name__]
      regex: ()
      action: keep

This is supported in agent's configmap and then configured in values.yaml

We have to pass the prometheus.yaml file through a variable

New or affected modules

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#167