[processor/k8sattributes] Refactor FieldExtractConfig

[dmitryax]

There are at least two issues with the current FieldExtractConfig config interface:

• [processor/k8sattributes] Deprecate and remove FieldExtractConfig.Regex config option #25128
• tag_name references the old "tag" concept inherited from OpenCensus, it should reference "attribute" or "resource attribute" instead.

Overall, the config should be aligned with all other filtering interfaces that we have in other parts of the Collector, which needs to be defined as part of #25161

[github-actions]

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