docs: update error-log-logger and datadog plugin docs

[Yilialinn]

Summary

• Update error-log-logger plugin doc: add canonical link, restructure attributes table with parent attributes, add examples section (TCP/SkyWalking/ClickHouse/Kafka), remove Delete Plugin section
• Update datadog plugin doc: add canonical link, add Metrics and Tags tables, add examples section, update attributes table with batch processor fields, remove Delete Plugin section

Both EN and ZH docs updated.

[Copilot]

Pull request overview

Updates the documentation for the error-log-logger and datadog plugins (English + Chinese), aligning the pages with the “hub” canonical URLs and expanding the configuration/explanation sections.

Changes:

• Added canonical links and refreshed plugin descriptions/front matter.
• Restructured configuration sections (attributes/metadata) and added richer usage examples.
• Updated exported metrics/tags documentation for the Datadog plugin and removed “Delete Plugin” sections.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 18 comments.

File	Description
docs/en/latest/plugins/error-log-logger.md	Adds canonical link, rewrites description and metadata table, and adds TCP/SkyWalking/ClickHouse/Kafka examples.
docs/zh/latest/plugins/error-log-logger.md	Same as EN, with updated Chinese description, metadata table, and examples.
docs/en/latest/plugins/datadog.md	Adds canonical link, reworks attributes/metadata, adds Metrics/Tags tables and examples.
docs/zh/latest/plugins/datadog.md	Same as EN, with updated Chinese structure and examples.

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[kayx23]

The Chinese datadog attributes table currently lists max_retry_count default as 60, but this setting comes from the batch processor wrapper and the actual default in apisix/utils/batch-processor.lua is 0. Could you update this value to avoid documenting a different retry policy than the code uses?

[kayx23]

The earlier datadog default issue looks fixed now, but the newer elasticsearch-logger docs seem to introduce a different docs/code mismatch: they document field.type and add it to example configs, while apisix/plugins/elasticsearch-logger.lua only defines field.index in the schema and does not accept a user-configurable field.type. The implementation only sets _type = "_doc" internally for ES 5/6 compatibility. Could you remove field.type from the docs/examples unless support is added in the plugin schema?