[WIP] Add Dynamic Schema support to StorageWriteToBigQuery

[jrmccluskey]

Implements support for using dynamic schemas in StorageWriteToBigQuery invocations.

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[jrmccluskey]

/gemini review

[gemini-code-assist]

Code Review

This pull request adds support for dynamic schemas and schema side inputs when writing to BigQuery using the Storage Write API (StorageWriteToBigQuery). It includes updates to handle callable schemas, passes schema side inputs through the pipeline, adds validation to ensure dynamic schemas are only used with dynamic destinations, and provides comprehensive unit and integration tests. There are no review comments, and the implementation looks solid, so I have no additional feedback to provide.

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