Implement flatbuffer interface in cpp parser

[melodyoncode]

New Features

• Configurable log levels for the C/C++ parser (error, warn, info, debug, trace) and structured logging with optional detailed entity-tree output at trace.
• Serialize cpp parser output to fbs.
• Add emit_debug_json to generate json files for debug.

Refactor

• PlantUML parser and metamodel reorganized: component/sequence/class types and resolvers updated; serializers and serialization artifacts split per diagram and relocated; build targets realigned.