Adds more SchemaFieldNumbers to classes used by Iceberg (#37055)

[chamikaramj]

Cherry-picks https://github.com/apache/beam/pull/37055 into the 2.70.0 release branch.

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[gemini-code-assist[bot]]

Summary of Changes

Hello @chamikaramj, I'm Gemini Code Assist[^1]! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request enhances the schema definition and serialization capabilities for Iceberg-related data structures within Apache Beam by adding explicit @SchemaFieldNumber annotations. This ensures consistent and robust schema evolution and data processing, particularly for the FileWriteResult and SerializableDataFile classes. This change is a cherry-pick from an earlier, related pull request.

Highlights

• Schema Field Numbering: Introduced @SchemaFieldNumber annotations to key methods within the FileWriteResult and SerializableDataFile classes.
• Improved Schema Definition: Explicitly assigned field numbers to all getter methods in SerializableDataFile (0-13) and to the two main getters in FileWriteResult (0-1), enhancing schema consistency and serialization.
• Iceberg Integration: These changes specifically target classes used in the Apache Beam Iceberg I/O connector, improving how data structures are represented and serialized for Iceberg tables.

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