feat(tag_cardinality_limit transform): enable per metric limits for tag_cardinality_limit

[esensar]

Summary

This adds the ability to add per metric limits in tag_cardinality_limit transform, besides the global configuration that applies to all metrics. It supports matching metrics by name and optionally by namespace too.

Change Type

• Bug fix
• New feature
• Non-functional (chore, refactoring, docs)
• Performance

Is this a breaking change?

• Yes
• No

How did you test this PR?

Added new tests to transforms::tag_cardinality_limits::tests and also tested manually with the following configuration:

sources:
  static_metrics_test:
    type: static_metrics
    interval_secs: 1
    metrics:
       - name: customA
         value:
           gauge:
             value: 3.0
         kind: absolute
         tags:
           custom_tag: custom_tag_1
           another_tag: test
       - name: customA
         value:
           gauge:
             value: 4.4
         kind: incremental
         tags:
           custom_tag: custom_tag_2
           another_tag: test
       - name: customA
         value:
           gauge:
             value: 4.4
         kind: incremental
         tags:
           custom_tag: custom_tag_3
           another_tag: test2
       - name: customB
         value:
           gauge:
             value: 3.0
         kind: absolute
         tags:
           custom_tag: custom_tag_1
           another_tag: test
       - name: customB
         value:
           gauge:
             value: 4.4
         kind: incremental
         tags:
           custom_tag: custom_tag_2
           another_tag: test
       - name: customB
         value:
           gauge:
             value: 4.4
         kind: incremental
         tags:
           custom_tag: custom_tag_3
           another_tag: test2

transforms:
  tag_cardinality:
    type: "tag_cardinality_limit"
    inputs: ["static_metrics_test"]
    value_limit: 2
    mode: "exact"
    per_metric_limits:
      - name: "customA"
        namespace: "static"
        value_limit: 5
        mode: "exact"

sinks:
  console:
    inputs: ["tag_cardinality"]
    target: "stdout"
    type: "console"
    acknowledgements:
      enabled: false
    encoding:
      codec: "json"

Confirmed that behavior is different for metricA and metricB (metricA didn't get its tags removed due to higher limit).

Does this PR include user facing changes?

• Yes. Please add a changelog fragment based on our guidelines.
• No. A maintainer will apply the "no-changelog" label to this PR.

Checklist

• Please read our Vector contributor resources.
• If this PR introduces changes Vector dependencies (modifies Cargo.lock), please
  run dd-rust-license-tool write to regenerate the license inventory and commit the changes (if any). More details here.

References

• Closes: Limit tag cardinality by metric in tag_cardinality_limit transform #15743
• Related: Add key_field option to tag_cardinality_limit #21112

[esensar]

I think this could also support #21112 with minor modifications, but I didn't go ahead with it right away, because I didn't want to introduce yet another level of nesting in the accepted_tags map. My idea was to reuse the key currently used for metric name for that custom key too, but that would mean changing the current metric name key to something that would hard to clash with when using custom keys. Not sure if it is a good idea.