[FLINK-40240][runtime] Support TRY_CAST, IFNULL and NULLIF in YAML Transform

[haruki-830]

Summary

This commit adds TRY_CAST, IFNULL, and NULLIF support to YAML Transform projections and filters. It aligns their behavior with Flink SQL while preserving the existing CAST failure semantics.

Key Changes

1. Function and Syntax Support

• Added operator and type metadata for TRY_CAST, IFNULL, and NULLIF.
• Added preprocessing for TRY_CAST(expr AS type) because Calcite 1.32 does not support this syntax directly.
• Handles nested expressions, different letter cases, quoted text, identifiers, and SQL comments.

2. Code Generation and Runtime Semantics

• Added Janino code generation for all three functions.
• TRY_CAST supports the same target types as the existing CAST implementation and returns NULL only for data conversion failures.
• Unsupported conversion paths fail during pipeline validation, while invalid configuration, UDF, and internal errors continue to fail the task.
• Added null-safe IFNULL and numeric-aware/deep-equality NULLIF evaluation without changing existing CAST behavior.

3. Test Coverage and Documentation

• Added parser, code generation, runtime, and YAML specification coverage for projections and filters.
• Covered successful and failed casts, nested expressions, nullability, invalid syntax, and function combinations.
• Verified the changes with both default Flink 1.20 and the Flink 2 profile.
• Updated the English and Chinese Transform documentation.

JIRA Reference

https://issues.apache.org/jira/browse/FLINK-40240

[haruki-830]

@lvyanquan @yuxiqian PTAL, thanks!