feat: Add option to automatically create per-event-type BigQuery views

[vasilyl]

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Link to Issue or Description of Change

1. Link to an existing issue (if applicable):

• Closes: N/A

2. Or, if no issue exists, describe the change:

Problem:
The BigQuery event log table consolidates diverse event types into a single schema where content payloads are serialized as raw JSON. Querying this raw table directly for specific event types is tedious and requires writing repetitive JSON extraction SQL queries.

Solution:
Add a configuration setting CreateViews (default true). When enabled, the plugin automatically and asynchronously creates simplified, typed BigQuery Views for each standard event type (e.g., v_user_message, v_model_request, v_tool_call). These views automatically extract JSON structures into clean, typed top-level columns (e.g., extracting prompts or tokens counts) for easy analytical querying.

Testing Plan

Added unit tests validating view creation queries are formulated correctly and executed asynchronously without blocking the main thread initialization.

Checklist

• I have read the CONTRIBUTING.md document.
• I have performed a self-review of my own code.
• I have commented my code, particularly in hard-to-understand areas.
• I have added tests that prove my fix is effective or that my feature works.
• New and existing unit tests pass locally with my changes.
• I have manually tested my changes end-to-end.