Internal support for parsing texture and normal indices in OBJ loader

[mehull-26]

Summary of Changes

This PR adds the ability to parse normals and texture coordinates from .obj files using the existing face parsing logic. This is currently internal-only, and not exposed in the documented API or parameter sets.

The goal is to fully integrate OBJ normal and texture support in a future PR, once the writer logic is updated, and a broader set of test cases are validated.

• Internal parsing logic implemented
• Unit test added for face parsing with v/vt/vn syntax
• Not exposed to public interface yet

Why not public yet?

• Writer does not yet support output of texture and normal attributes.
• Further edge case testing is necessary before public exposure.

Once these conditions are met, the feature will be promoted to the public API.

Release Management

• Affected package(s): Stream Support
• Issue(s) solved (if any): partially worked on #8344
• Feature/Small Feature (if any): added capability of reading normals and texture coordinates in OBJ file format (not yet exposed to public API though, only kept to internal::read_obj() )
• Link to compiled documentation (obligatory for small feature) Not yet exposed to the public API to write documentation for
• License and copyright ownership: Same as CGAL

[mehull-26]

Updated it with a cleaner PR : #8857