fix(ai-gateway): Decouple otel data and icnludes from API Gateway

[tomek-labuk]

Description

Fixes #issue

Preview Links

Checklist

• Tested how-to docs. If not, note why here.
• All pages contain metadata.
• Any new docs link to existing docs.
• All autogenerated instructions render correctly (API, decK, Konnect, Kong Manager).
• Style guide (capitalized gateway entities, placeholder URLs) implemented correctly.
• Every page has a description entry in frontmatter.
• Add new pages to the product documentation index (if applicable).

[Copilot]

✅ Ready to approve

The changes are a straightforward docs refactor with new AI Gateway–scoped includes/data, and the Liquid/YAML patterns match existing, already-used include implementations in the repo.

Note: this review does not count toward required approvals for merging.

Pull request overview

This PR refactors the AI Gateway OpenTelemetry reference docs to source span attribute and metric tables from AI Gateway–specific data/includes rather than reusing API Gateway (plugin) include/data files, helping decouple the documentation paths and content ownership.

Changes:

• Updated AI Gateway docs to include AI Gateway–scoped span attribute and metric table includes.
• Added new reusable include partials to render span attribute and metric tables from AI Gateway data files.
• Introduced new AI Gateway v2 YAML datasets for OTel span attributes and metrics (including attribute descriptions).

File summaries

File	Description
app/ai-gateway/llm-open-telemetry.md	Switches the span attribute table include to the AI Gateway–scoped partial.
app/ai-gateway/ai-otel-metrics.md	Replaces large inline metric documentation blocks with AI Gateway–scoped metric table includes and a brief note for kong.gen_ai.llm.cost.
app/_includes/md/ai-gateway/v2/policies/span_attribute_tables.md	New include to render span attribute reference sections from AI Gateway YAML data.
app/_includes/md/ai-gateway/v2/policies/metric_tables.md	New include to render metric reference sections from AI Gateway YAML data with prefix filtering.
app/_includes/md/ai-gateway/v2/policies/collecting-otel-data.md	Adds an AI Gateway–scoped “Collecting telemetry data” include block for policy docs.
app/_data/ai-gateway/v2/otel-span-attributes.yaml	New dataset defining AI Gateway span groups and attribute descriptions.
app/_data/ai-gateway/v2/otel-metrics.yaml	New dataset defining AI Gateway metrics and attribute descriptions.

Copilot's findings

• Files reviewed: 7/7 changed files
• Comments generated: 0

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[jbaross]

LGTM