feat: Add dns_sd_configs to ScrapeConfig

[slashpai]

Fixes #5862

Test manually and it works. Added e2e test as well

Example:

apiVersion: monitoring.coreos.com/v1alpha1
kind: ScrapeConfig
metadata:
  name: scrape-config-dns-sd-example
  namespace: default
  labels:
    app.kubernetes.io/name: scrape-config-dns-sd-example
spec:
  dnsSDConfigs:
    - names:
      - demo.do.prometheus.io
      type: A
      port: 9090
    - names:
      - node.demo.do.prometheus.io
      type: A
      port: 9100

Description

Describe the big picture of your changes here to communicate to the maintainers why we should accept this pull request.
If it fixes a bug or resolves a feature request, be sure to link to that issue.

Add DNSSDConfigs to ScrapeConfig

Type of change

What type of changes does your code introduce to the Prometheus operator? Put an x in the box that apply.

• CHANGE (fix or feature that would cause existing functionality to not work as expected)
• FEATURE (non-breaking change which adds functionality)
• BUGFIX (non-breaking change which fixes an issue)
• ENHANCEMENT (non-breaking change which improves existing functionality)
• NONE (if none of the other choices apply. Example, tooling, build system, CI, docs, etc.)

Changelog entry

Please put a one-line changelog entry below. This will be copied to the changelog file during the release process.

Add dns_sd_configs to ScrapeConfig CRD

[slashpai]

Moving to draft since need to test rejected resources as well

[slashpai]

Moving to draft since need to test rejected resources as well

This is done. Added test for resource selection as well

[slashpai]

cc: @simonpasquier

[slashpai]

@simonpasquier Addressed comments

[simonpasquier]

Thanks!