feat(anthropic): support user_id metadata tag

[emhagman]

Summary

Add tag support for metdata.user_id in Anthropic message calls (seen here https://docs.anthropic.com/en/api/messages#body-metadata) so that you can filter traces by user_id properly.

Currently anthropic.request.paramters contains a string of the dict which can't be filtered. Similar to user being tracked as a tag in openai.request.user but for Anthropic.

Risks

See PR comment; Removes user_id from anthropic.request.params based on how it's coded. If people have trace filters, APM Metrics, etc by looking for user_id in their string already, it would break that. We could keep it in there for legacy reasons if needed.

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[emhagman]

This does remove it from anthropic.request.params, not sure if we should include it for legacy reasons in case anyone was using string matching here in their traces (@anthropic.request.params:"...") or if it's OK to change this.

[github-actions]

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