- Introduce IdVisitor for schema traversal to init id_to_index_(Map)
- Introduce NameVisitor for schema traversal to init name_to_index_(Map), lowercase_name_to_index_(map)

…ava impl

1. Refactor IdVisitor: Add VisitNested() to handle NestedType, make Visit() generic for all Type hierarchy (avoid anti-pattern)
2. Merge id_to_index_ + full_schemafield_ into id_to_field_ (std::unordered_map<int32_t, const ref<SchemaField>>) to reduce memory footprint
3. Align with Java impl's idToField design (support future alias/identifier fields without refactor)

- change the type of id from size_t to int_32
- rename GetPath to BuildPath
- fix bug new_short_path should build from short_path, not path

…sult call in macros

- Added logic to detect and handle duplicate names in NameToIdVisitor to prevent invalid schema errors.
- Fixed duplicate result call issue in src/iceberg/util/macros.h by optimizing ICEBERG_RETURN_UNEXPECTED macro.

… conversion function

- Implemented detection for duplicate field IDs, Names in visitors, returning kInvalidSchema error with message.
- Updated lowercase conversion in NameToIdVisitor

…reduce copies and unify initialization

- Switched field_ and schema_ members in test classes to std::unique_ptr for unique ownership and to avoid duplicate and avoid creating duplicate objects.

… std::string creation