[corechecks/snmp] Fix format config for column metric tags

[AlexandreYang]

What does this PR do?

Fix format config to work with column metrics tags.

For example: https://github.com/DataDog/integrations-core/pull/11871/files#diff-7031715b315cd7cb4e97c40e1d0325fb47b864e970868d6c4b5438e9b9602bf2R27-R31

metrics:
  - MIB: MERAKI-CLOUD-CONTROLLER-MIB
    table:
      OID: 1.3.6.1.4.1.29671.1.1.4
      name: devTable
      # devTable INDEX is: devMac
    forced_type: gauge
    symbols:
      - OID: 1.3.6.1.4.1.29671.1.1.4.1.3
        name: devStatus
      - OID: 1.3.6.1.4.1.29671.1.1.4.1.5
        name: devClientCount
    metric_tags:
      # devMac is part of the devTable index
      - column:
          OID: 1.3.6.1.4.1.29671.1.1.4.1.1
          name: devMac
          format: mac_address
        tag: mac_address
      - column:
          OID: 1.3.6.1.4.1.29671.1.1.4.1.2
          name: devName
        tag: device
      - column:
          OID: 1.3.6.1.4.1.29671.1.1.4.1.9
          name: devProductCode
        tag: product
      - column:
          OID: 1.3.6.1.4.1.29671.1.1.4.1.11
          name: devNetworkName
        tag: network

Motivation

1/ bug fix for #11557

2/ needed for DataDog/integrations-core#11871

Additional Notes

Possible Drawbacks / Trade-offs

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• If applicable, the config template has been updated.

[AlexandreYang]

Note for reviewers: GetTags has been moved to report_utils.go and renamed to getTagsFromMetricTagConfigList

Same for transformIndex

[FlorianVeaux]

Just to make sure I understood this PR correctly, there is some refactoring but the only real change in behavior is that we now use getColumnValuesFromSymbol in the function getTagsFromMetricTagConfigList instead of using values.GetColumnValues ?
Can you confirm my understanding is correct and I haven't missed any other change in the refactor?

[AlexandreYang]

@FlorianVeaux Your understanding is correct. Sorry, I should have detailed that in the first place.

[FlorianVeaux]

Mostly a refactor and test, the one-line behavior change looks good to me if CI is green 👍
Thanks!