[IcebergIO] Support TableIdentifiers with special characters

[ahmedabu98]

An attempt at a more efficient replication of #33293, which had some performance issues because it was eagerly parsing with JSON, and was reverted in #33575.

This PR only does JSON parsing when the table id has JSON-like characters or a dot in the namespace / name.

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Summary of Changes

Hello, I'm Gemini Code Assist¹! 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 improves the handling of Iceberg table identifiers in the Beam Iceberg IO connector. By introducing a conditional JSON parsing strategy, it enables support for table names and namespaces containing dots or other special characters while avoiding the performance overhead of eager JSON parsing for standard identifiers. This change ensures robust compatibility with complex table naming conventions.

Highlights

• Improved TableIdentifier Parsing: Introduced IcebergUtils.parseTableIdentifier and IcebergUtils.tableIdentifierToString to handle Iceberg table identifiers containing special characters like dots, using JSON serialization only when necessary to maintain performance.
• Refactored IO Classes: Updated multiple Iceberg IO classes (AddFiles, AppendFilesToTables, AssignDestinationsAndPartitions, etc.) to use the new utility methods instead of direct TableIdentifier.parse calls.
• Enhanced Test Coverage: Added comprehensive unit tests in IcebergUtilsTest to verify correct parsing and round-tripping of table identifiers with special characters.

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[ahmedabu98]

R: @regadas

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Code Review

This pull request introduces utility methods in IcebergUtils (tableIdentifierToString and parseTableIdentifier) to safely serialize and parse Iceberg TableIdentifiers, preventing issues with special characters like dots by utilizing JSON serialization when necessary. These utilities are integrated across multiple Iceberg IO components, and corresponding tests are updated. The review feedback highlights a potential bug in startsWithJsonObject where legacy identifiers starting with '{' but not ending with '}' (e.g., '{dogs}.food') would be incorrectly parsed as JSON. The reviewer suggests a more robust check that verifies both the starting and ending characters, along with updating the test suite to cover this scenario.

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