Add lint/ordering validation for metadata.yaml in mdatagen

[paulojmdias]

Component(s)

No response

Describe the issue you're reporting

Following this comment: open-telemetry/opentelemetry-collector-contrib#42477 (comment)

mdatagen should validate that keys inside metadata.yaml are sorted consistently. For example:
• resource_attributes
• attributes
• metrics
• events
• telemetry.metrics

This would reduce noisy diffs and keep files consistent across components.

Tip

_{React with 👍 to help prioritize this issue. Please use comments to provide useful context, avoiding +1 or me too, to help us triage it. Learn more here.}

[paulojmdias]

/label cmd/mdatagen

[github-actions]

Pinging code owners for cmd/mdatagen: @dmitryax. See Adding Labels via Comments if you do not have permissions to add labels yourself. For example, comment '/label priority:p2 -needs-triaged' to set the priority and remove the needs-triaged label.