[Xlang] Fory Scheam IDL parser and compiler

[chaokunyang]

Feature Request

Add Fory Scheam IDL(FDL) parser and compiler.

The FDL compiler generates cross-language serialization code from schema definitions. It enables type-safe cross-language data exchange by generating native data structures with Fory serialization support for multiple programming languages.

Features:

• Multi-language code generation: Java, Python, Go, Rust, C++
• Rich type system: Primitives, enums, messages, lists, maps
• Cross-language serialization: Generated code works seamlessly with Apache Fory
• Type ID and namespace support: Both numeric IDs and name-based type registration
• Field modifiers: Optional fields, reference tracking, repeated fields
• File imports: Modular schemas with import support
• Protobuffer IDL support: Make FDL compiler support parse protobuf schema proto files, and generate struct code.
• Flatbuffer IDL support: Make FDL compiler support parse flafbuffer schema fbs files, and generate struct code.
• Unsigned number support: Protobuffer/Flatbuffer all support unsigned numer
• OneOf/Union support: Support Protobuffer OneOf scheam and Flatbuffer union schema

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